diff --git a/eng/common-tests/ChangeLog-Operations.Tests.ps1 b/eng/common-tests/ChangeLog-Operations.Tests.ps1
new file mode 100644
index 00000000000..2a406e80aff
--- /dev/null
+++ b/eng/common-tests/ChangeLog-Operations.Tests.ps1
@@ -0,0 +1,227 @@
+Import-Module Pester
+
+BeforeAll {
+    . $PSScriptRoot/../common/scripts/ChangeLog-Operations.ps1
+}
+
+Describe "Parse-ChangelogContent" {
+    It "Should parse changelog text with multiple sections" {
+        $changelogText = "### Breaking Changes`n`n- Removed deprecated API ``oldMethod()```n- Changed return type of ``getData()```n`n### Features Added`n`n- Added new ``newMethod()`` API`n- Added support for async operations`n`n### Bugs Fixed`n`n- Fixed null pointer exception in ``processData()``"
+
+        $result = Parse-ChangelogContent -ChangelogText $changelogText -InitialAtxHeader "#"
+
+        $result | Should -Not -BeNullOrEmpty
+        $result.ReleaseContent | Should -Not -BeNullOrEmpty
+        $result.Sections | Should -Not -BeNullOrEmpty
+        $result.Sections.Keys | Should -HaveCount 3
+        $result.Sections.ContainsKey("Breaking Changes") | Should -BeTrue
+        $result.Sections.ContainsKey("Features Added") | Should -BeTrue
+        $result.Sections.ContainsKey("Bugs Fixed") | Should -BeTrue
+    }
+
+    It "Should handle single section changelog" {
+        $changelogText = "### Features Added`n`n- Added new feature X`n- Added new feature Y"
+
+        $result = Parse-ChangelogContent -ChangelogText $changelogText -InitialAtxHeader "#"
+
+        $result | Should -Not -BeNullOrEmpty
+        $result.Sections.Keys | Should -HaveCount 1
+        $result.Sections.ContainsKey("Features Added") | Should -BeTrue
+        $result.Sections["Features Added"] | Should -Contain ""
+        $result.Sections["Features Added"] | Should -Contain "- Added new feature X"
+        $result.Sections["Features Added"] | Should -Contain "- Added new feature Y"
+    }
+
+    It "Should handle empty changelog text sections with content before first section" {
+        $changelogText = "Some introductory text`n`n### Breaking Changes`n`n- Change 1"
+
+        $result = Parse-ChangelogContent -ChangelogText $changelogText -InitialAtxHeader "#"
+
+        $result | Should -Not -BeNullOrEmpty
+        $result.Sections.Keys | Should -HaveCount 1
+        # The intro text should be in ReleaseContent but not in any section
+        $result.ReleaseContent | Should -Contain "Some introductory text"
+    }
+
+    It "Should respect InitialAtxHeader parameter" {
+        # With ## as initial header, section headers are ####
+        $changelogText = "#### Breaking Changes`n`n- Some breaking change"
+
+        $result = Parse-ChangelogContent -ChangelogText $changelogText -InitialAtxHeader "##"
+
+        $result | Should -Not -BeNullOrEmpty
+        $result.Sections.Keys | Should -HaveCount 1
+        $result.Sections.ContainsKey("Breaking Changes") | Should -BeTrue
+    }
+
+    It "Should return empty sections when no section headers found" {
+        $changelogText = "Just some text without any section headers`nAnd another line"
+
+        $result = Parse-ChangelogContent -ChangelogText $changelogText -InitialAtxHeader "#"
+
+        $result | Should -Not -BeNullOrEmpty
+        $result.Sections.Keys | Should -HaveCount 0
+        $result.ReleaseContent | Should -Not -BeNullOrEmpty
+    }
+
+    It "Should handle Windows-style line endings" {
+        $changelogText = "### Features Added`r`n`r`n- Feature 1`r`n- Feature 2"
+
+        $result = Parse-ChangelogContent -ChangelogText $changelogText -InitialAtxHeader "#"
+
+        $result | Should -Not -BeNullOrEmpty
+        $result.Sections.ContainsKey("Features Added") | Should -BeTrue
+    }
+
+    It "Should handle Unix-style line endings" {
+        $changelogText = "### Features Added`n`n- Feature 1`n- Feature 2"
+
+        $result = Parse-ChangelogContent -ChangelogText $changelogText -InitialAtxHeader "#"
+
+        $result | Should -Not -BeNullOrEmpty
+        $result.Sections.ContainsKey("Features Added") | Should -BeTrue
+    }
+}
+
+Describe "Set-ChangeLogEntryContent" {
+    It "Should update changelog entry with new content" {
+        # Create a mock changelog entry
+        $entry = [PSCustomObject]@{
+            ReleaseVersion = "1.0.0"
+            ReleaseStatus = "(Unreleased)"
+            ReleaseTitle = "## 1.0.0 (Unreleased)"
+            ReleaseContent = @()
+            Sections = @{}
+        }
+
+        $newContent = "### Features Added`n`n- Added new feature A`n- Added new feature B"
+
+        $result = Set-ChangeLogEntryContent -ChangeLogEntry $entry -NewContent $newContent -InitialAtxHeader "#"
+
+        $result | Should -Not -BeNullOrEmpty
+        $result.ReleaseContent | Should -Not -BeNullOrEmpty
+        $result.Sections.ContainsKey("Features Added") | Should -BeTrue
+        $result.Sections["Features Added"] | Should -Contain "- Added new feature A"
+        $result.Sections["Features Added"] | Should -Contain "- Added new feature B"
+    }
+
+    It "Should replace existing content in changelog entry" {
+        # Create a mock changelog entry with existing content
+        $entry = [PSCustomObject]@{
+            ReleaseVersion = "1.0.0"
+            ReleaseStatus = "(Unreleased)"
+            ReleaseTitle = "## 1.0.0 (Unreleased)"
+            ReleaseContent = @("", "### Old Section", "", "- Old content")
+            Sections = @{
+                "Old Section" = @("", "- Old content")
+            }
+        }
+
+        $newContent = "### Breaking Changes`n`n- New breaking change"
+
+        $result = Set-ChangeLogEntryContent -ChangeLogEntry $entry -NewContent $newContent -InitialAtxHeader "#"
+
+        $result | Should -Not -BeNullOrEmpty
+        $result.Sections.ContainsKey("Breaking Changes") | Should -BeTrue
+        $result.Sections.ContainsKey("Old Section") | Should -BeFalse
+    }
+
+    It "Should use default InitialAtxHeader when not specified" {
+        $entry = [PSCustomObject]@{
+            ReleaseVersion = "1.0.0"
+            ReleaseStatus = "(Unreleased)"
+            ReleaseTitle = "## 1.0.0 (Unreleased)"
+            ReleaseContent = @()
+            Sections = @{}
+        }
+
+        $newContent = "### Features Added`n`n- Feature 1"
+
+        $result = Set-ChangeLogEntryContent -ChangeLogEntry $entry -NewContent $newContent
+
+        $result | Should -Not -BeNullOrEmpty
+        $result.Sections.ContainsKey("Features Added") | Should -BeTrue
+    }
+}
+
+Describe "Integration: Update Changelog Entry and Write Back" {
+    BeforeEach {
+        # Create a temporary changelog file for integration testing
+        $script:tempChangelogPath = Join-Path ([System.IO.Path]::GetTempPath()) "CHANGELOG_$([System.Guid]::NewGuid().ToString()).md"
+        
+        $initialChangelog = @"
+# Release History
+
+## 1.0.0 (Unreleased)
+
+### Features Added
+
+### Breaking Changes
+
+### Bugs Fixed
+
+## 0.9.0 (2024-01-15)
+
+### Features Added
+
+- Initial release feature
+"@
+        Set-Content -Path $script:tempChangelogPath -Value $initialChangelog
+    }
+
+    AfterEach {
+        if (Test-Path $script:tempChangelogPath) {
+            Remove-Item -Path $script:tempChangelogPath -Force -ErrorAction SilentlyContinue
+        }
+    }
+
+    It "Should update changelog file through the full workflow" {
+        # Get existing entries
+        $entries = Get-ChangeLogEntries -ChangeLogLocation $script:tempChangelogPath
+        $entries | Should -Not -BeNullOrEmpty
+
+        # Get the unreleased entry
+        $unreleasedEntry = $entries["1.0.0"]
+        $unreleasedEntry | Should -Not -BeNullOrEmpty
+        $unreleasedEntry.ReleaseStatus | Should -Be "(Unreleased)"
+
+        # Prepare new content
+        $newContent = "### Breaking Changes`n`n- Removed deprecated method ``oldApi()```n- Changed signature of ``processData()```n`n### Features Added`n`n- Added async support for all operations`n- Added new ``streamData()`` method"
+
+        # Update the entry content
+        Set-ChangeLogEntryContent -ChangeLogEntry $unreleasedEntry -NewContent $newContent -InitialAtxHeader $entries.InitialAtxHeader
+
+        # Write back to file
+        Set-ChangeLogContent -ChangeLogLocation $script:tempChangelogPath -ChangeLogEntries $entries
+
+        # Verify the file was updated correctly
+        $updatedContent = Get-Content -Path $script:tempChangelogPath -Raw
+        $updatedContent | Should -Match "Removed deprecated method"
+        $updatedContent | Should -Match "Added async support"
+        $updatedContent | Should -Match "streamData"
+
+        # Verify the structure is still valid
+        $updatedEntries = Get-ChangeLogEntries -ChangeLogLocation $script:tempChangelogPath
+        $updatedEntries | Should -Not -BeNullOrEmpty
+        $updatedEntries["1.0.0"].Sections.ContainsKey("Breaking Changes") | Should -BeTrue
+        $updatedEntries["1.0.0"].Sections.ContainsKey("Features Added") | Should -BeTrue
+    }
+
+    It "Should preserve other versions when updating one version" {
+        $entries = Get-ChangeLogEntries -ChangeLogLocation $script:tempChangelogPath
+        
+        $unreleasedEntry = $entries["1.0.0"]
+        $newContent = "### Features Added`n`n- New feature"
+        
+        Set-ChangeLogEntryContent -ChangeLogEntry $unreleasedEntry -NewContent $newContent -InitialAtxHeader $entries.InitialAtxHeader
+        Set-ChangeLogContent -ChangeLogLocation $script:tempChangelogPath -ChangeLogEntries $entries
+
+        # Verify the old version is still present
+        $updatedContent = Get-Content -Path $script:tempChangelogPath -Raw
+        $updatedContent | Should -Match "0.9.0"
+        $updatedContent | Should -Match "Initial release feature"
+
+        $updatedEntries = Get-ChangeLogEntries -ChangeLogLocation $script:tempChangelogPath
+        $updatedEntries["0.9.0"] | Should -Not -BeNullOrEmpty
+    }
+}
diff --git a/eng/common/scripts/ChangeLog-Operations.ps1 b/eng/common/scripts/ChangeLog-Operations.ps1
index c5c4f5ed20c..170157ff511 100644
--- a/eng/common/scripts/ChangeLog-Operations.ps1
+++ b/eng/common/scripts/ChangeLog-Operations.ps1
@@ -8,6 +8,15 @@ $CHANGELOG_UNRELEASED_STATUS = "(Unreleased)"
 $CHANGELOG_DATE_FORMAT = "yyyy-MM-dd"
 $RecommendedSectionHeaders = @("Features Added", "Breaking Changes", "Bugs Fixed", "Other Changes")
 
+# Helper function to build the section header regex pattern
+function Get-SectionHeaderRegex {
+  param(
+    [Parameter(Mandatory = $true)]
+    [string]$InitialAtxHeader
+  )
+  return "^${InitialAtxHeader}${SECTION_HEADER_REGEX_SUFFIX}"
+}
+
 # Returns a Collection of changeLogEntry object containing changelog info for all versions present in the gived CHANGELOG
 function Get-ChangeLogEntries {
   param (
@@ -49,7 +58,7 @@ function Get-ChangeLogEntriesFromContent {
     $initialAtxHeader = $matches["HeaderLevel"]
   }
 
-  $sectionHeaderRegex = "^${initialAtxHeader}${SECTION_HEADER_REGEX_SUFFIX}"
+  $sectionHeaderRegex = Get-SectionHeaderRegex -InitialAtxHeader $initialAtxHeader
   $changeLogEntries | Add-Member -NotePropertyName "InitialAtxHeader" -NotePropertyValue $initialAtxHeader
   $releaseTitleAtxHeader = $initialAtxHeader + "#"
   $headerLines = @()
@@ -301,7 +310,7 @@ function Remove-EmptySections {
     $InitialAtxHeader = "#"
   )
 
-  $sectionHeaderRegex = "^${InitialAtxHeader}${SECTION_HEADER_REGEX_SUFFIX}"
+  $sectionHeaderRegex = Get-SectionHeaderRegex -InitialAtxHeader $InitialAtxHeader
   $releaseContent = $ChangeLogEntry.ReleaseContent
 
   if ($releaseContent.Count -gt 0)
@@ -460,3 +469,135 @@ function Confirm-ChangeLogForRelease {
   }
   return $ChangeLogStatus.IsValid
 }
+
+function Parse-ChangelogContent {
+  <#
+  .SYNOPSIS
+      Parses raw changelog text into structured content with sections.
+  
+  .DESCRIPTION
+      Takes raw changelog text and parses it into structured arrays containing
+      ReleaseContent (all lines) and Sections (organized by section headers).
+      This function only generates content structure without modifying any files.
+  
+  .PARAMETER ChangelogText
+      The new changelog text containing sections (e.g., "### Breaking Changes", "### Features Added").
+  
+  .PARAMETER InitialAtxHeader
+      The markdown header level used in the changelog (e.g., "#" for H1, "##" for H2).
+      Defaults to "#".
+  
+  .OUTPUTS
+      PSCustomObject with ReleaseContent and Sections properties.
+  
+  .EXAMPLE
+      $content = Parse-ChangelogContent -ChangelogText $changelogText -InitialAtxHeader "#"
+      $content.ReleaseContent # Array of all lines
+      $content.Sections # Hashtable of section name to content lines
+  #>
+  [CmdletBinding()]
+  param(
+    [Parameter(Mandatory = $true)]
+    [ValidateNotNullOrEmpty()]
+    [string]$ChangelogText,
+    
+    [Parameter(Mandatory = $false)]
+    [ValidateNotNullOrEmpty()]
+    [string]$InitialAtxHeader = "#"
+  )
+  
+  Write-Verbose "Parsing changelog text into structured content..."
+  
+  # Parse the new changelog content into lines
+  $changelogLines = $ChangelogText -split "`r?`n"
+  
+  # Initialize content structure
+  $releaseContent = @()
+  $sections = @{}
+  
+  # Add an empty line after the version header
+  $releaseContent += ""
+  
+  # Parse the changelog content
+  # InitialAtxHeader represents the markdown header level (e.g., "#" for H1, "##" for H2)
+  # Section headers are two levels deeper than the changelog title
+  # (e.g., "### Breaking Changes" if InitialAtxHeader is "#")
+  $currentSection = $null
+  $sectionHeaderRegex = Get-SectionHeaderRegex -InitialAtxHeader $InitialAtxHeader
+  
+  foreach ($line in $changelogLines) {
+    if ($line.Trim() -match $sectionHeaderRegex) {
+      $currentSection = $matches["sectionName"].Trim()
+      $sections[$currentSection] = @()
+      $releaseContent += $line
+      Write-Verbose "  Found section: $currentSection"
+    }
+    elseif ($currentSection) {
+      $sections[$currentSection] += $line
+      $releaseContent += $line
+    }
+    else {
+      $releaseContent += $line
+    }
+  }
+  
+  Write-Verbose "  Parsed $($sections.Count) section(s)"
+  
+  # Return structured content
+  return [PSCustomObject]@{
+    ReleaseContent = $releaseContent
+    Sections = $sections
+  }
+}
+
+function Set-ChangeLogEntryContent {
+  <#
+  .SYNOPSIS
+      Updates a changelog entry with new content.
+  
+  .DESCRIPTION
+      Takes a changelog entry object and new changelog text, parses the text into
+      structured content, and updates the entry's ReleaseContent and Sections properties.
+  
+  .PARAMETER ChangeLogEntry
+      The changelog entry object to update (from Get-ChangeLogEntries).
+  
+  .PARAMETER NewContent
+      The new changelog text containing sections.
+  
+  .PARAMETER InitialAtxHeader
+      The markdown header level used in the changelog. Defaults to "#".
+  
+  .OUTPUTS
+      The updated changelog entry object.
+  
+  .EXAMPLE
+      $entries = Get-ChangeLogEntries -ChangeLogLocation $changelogPath
+      $entry = $entries["1.0.0"]
+      Set-ChangeLogEntryContent -ChangeLogEntry $entry -NewContent $newText -InitialAtxHeader $entries.InitialAtxHeader
+      Set-ChangeLogContent -ChangeLogLocation $changelogPath -ChangeLogEntries $entries
+  #>
+  [CmdletBinding()]
+  param(
+    [Parameter(Mandatory = $true)]
+    [ValidateNotNull()]
+    [PSCustomObject]$ChangeLogEntry,
+    
+    [Parameter(Mandatory = $true)]
+    [ValidateNotNullOrEmpty()]
+    [string]$NewContent,
+    
+    [Parameter(Mandatory = $false)]
+    [ValidateNotNullOrEmpty()]
+    [string]$InitialAtxHeader = "#"
+  )
+  
+  # Parse the new content into structured format
+  $parsedContent = Parse-ChangelogContent -ChangelogText $NewContent -InitialAtxHeader $InitialAtxHeader
+  
+  # Update the entry with the parsed content
+  $ChangeLogEntry.ReleaseContent = $parsedContent.ReleaseContent
+  $ChangeLogEntry.Sections = $parsedContent.Sections
+  
+  return $ChangeLogEntry
+}