diff --git a/TUnit.Analyzers.CodeFixers/Base/TwoPhase/ConversionPlan.cs b/TUnit.Analyzers.CodeFixers/Base/TwoPhase/ConversionPlan.cs
index 9dd2aa3d5b..3983091e31 100644
--- a/TUnit.Analyzers.CodeFixers/Base/TwoPhase/ConversionPlan.cs
+++ b/TUnit.Analyzers.CodeFixers/Base/TwoPhase/ConversionPlan.cs
@@ -483,9 +483,15 @@ public class InvocationReplacement : ConversionTarget
 public class TheoryDataConversion : ConversionTarget
 {
     /// <summary>
-    /// The element type(s) from TheoryData&lt;T&gt; (e.g., "TimeSpan" from TheoryData&lt;TimeSpan&gt;)
+    /// The individual type arguments from TheoryData (e.g., ["TimeSpan"] or ["string", "int"]).
     /// </summary>
-    public required string ElementType { get; init; }
+    public required IReadOnlyList<string> ElementTypes { get; init; }
+
+    /// <summary>
+    /// Whether the TheoryData has multiple type arguments (e.g., TheoryData&lt;string, int&gt;).
+    /// When true, initializer expressions { val1, val2 } must be converted to tuple expressions (val1, val2).
+    /// </summary>
+    public bool IsMultiType => ElementTypes.Count > 1;
 
     /// <summary>
     /// Annotation for the GenericName (TheoryData&lt;T&gt;) type syntax to convert to IEnumerable&lt;T&gt;
diff --git a/TUnit.Analyzers.CodeFixers/Base/TwoPhase/MigrationTransformer.cs b/TUnit.Analyzers.CodeFixers/Base/TwoPhase/MigrationTransformer.cs
index d9bb94f30c..2d0d1488ad 100644
--- a/TUnit.Analyzers.CodeFixers/Base/TwoPhase/MigrationTransformer.cs
+++ b/TUnit.Analyzers.CodeFixers/Base/TwoPhase/MigrationTransformer.cs
@@ -229,9 +229,12 @@ private CompilationUnitSyntax TransformTheoryData(CompilationUnitSyntax root)
 
                     if (objectCreation?.Initializer != null)
                     {
-                        // Build array type: T[]
+                        // Build the element type: T for single, (T1, T2) for multi
+                        var elementTypeSyntax = BuildElementType(conversion.ElementTypes);
+
+                        // Build array type: T[] or (T1, T2)[]
                         var arrayType = SyntaxFactory.ArrayType(
-                            SyntaxFactory.ParseTypeName(conversion.ElementType),
+                            elementTypeSyntax,
                             SyntaxFactory.SingletonList(
                                 SyntaxFactory.ArrayRankSpecifier(
                                     SyntaxFactory.SingletonSeparatedList<ExpressionSyntax>(
@@ -241,21 +244,40 @@ private CompilationUnitSyntax TransformTheoryData(CompilationUnitSyntax root)
                             )
                         ).WithoutTrailingTrivia();
 
-                        // Get the open brace token and ensure it has proper newline trivia
+                        // Get the open brace token and ensure it has proper newline trivia.
+                        // When the brace is on a separate line (e.g., new Type\n{), the newline
+                        // may be trailing trivia of the preceding token, not leading trivia of {.
+                        // Preserve existing whitespace indentation when adding the newline.
                         var openBrace = objectCreation.Initializer.OpenBraceToken;
                         if (!openBrace.LeadingTrivia.Any(t => t.IsKind(SyntaxKind.EndOfLineTrivia)))
                         {
-                            // Add newline and proper indentation before the brace
+                            var existingWhitespace = openBrace.LeadingTrivia
+                                .LastOrDefault(t => t.IsKind(SyntaxKind.WhitespaceTrivia));
+
+                            var whitespace = existingWhitespace.IsKind(SyntaxKind.WhitespaceTrivia)
+                                ? existingWhitespace
+                                : SyntaxFactory.Whitespace("    ");
+
                             openBrace = openBrace.WithLeadingTrivia(
                                 SyntaxFactory.EndOfLine("\n"),
-                                SyntaxFactory.Whitespace("    "));
+                                whitespace);
+                        }
+
+                        // For multi-type TheoryData, convert complex initializer expressions
+                        // { val1, val2 } to tuple expressions (val1, val2)
+                        var expressions = objectCreation.Initializer.Expressions;
+                        if (conversion.IsMultiType)
+                        {
+                            expressions = SyntaxFactory.SeparatedList(
+                                expressions.Select(expr => ConvertToTupleExpression(expr)),
+                                expressions.GetSeparators());
                         }
 
                         // Create array initializer from the collection initializer
                         var newInitializer = SyntaxFactory.InitializerExpression(
                             SyntaxKind.ArrayInitializerExpression,
                             openBrace,
-                            objectCreation.Initializer.Expressions,
+                            expressions,
                             objectCreation.Initializer.CloseBraceToken);
 
                         // Build the array creation expression
@@ -273,7 +295,7 @@ private CompilationUnitSyntax TransformTheoryData(CompilationUnitSyntax root)
                     }
                 }
 
-                // Then, transform the type declaration from TheoryData<T> to IEnumerable<T>
+                // Then, transform the type declaration from TheoryData<T> to IEnumerable<T> or IEnumerable<(T1, T2)>
                 if (conversion.TypeAnnotation != null)
                 {
                     var genericName = currentRoot.DescendantNodes()
@@ -282,10 +304,13 @@ private CompilationUnitSyntax TransformTheoryData(CompilationUnitSyntax root)
 
                     if (genericName != null)
                     {
+                        var elementTypeSyntax = BuildElementType(conversion.ElementTypes);
+                        var typeArgList = SyntaxFactory.TypeArgumentList(
+                            SyntaxFactory.SingletonSeparatedList(elementTypeSyntax));
+
                         var enumerableType = SyntaxFactory.GenericName(
                             SyntaxFactory.Identifier("IEnumerable"),
-                            SyntaxFactory.TypeArgumentList(
-                                SyntaxFactory.SeparatedList(genericName.TypeArgumentList.Arguments)))
+                            typeArgList)
                             .WithLeadingTrivia(genericName.GetLeadingTrivia())
                             .WithTrailingTrivia(genericName.GetTrailingTrivia());
 
@@ -308,6 +333,47 @@ private CompilationUnitSyntax TransformTheoryData(CompilationUnitSyntax root)
         return currentRoot;
     }
 
+    /// <summary>
+    /// Builds the element TypeSyntax from the stored type argument strings.
+    /// Single type: returns the type directly (e.g., "TimeSpan" → TimeSpan).
+    /// Multi type: returns a tuple type (e.g., ["string", "int"] → (string, int)).
+    /// </summary>
+    private static TypeSyntax BuildElementType(IReadOnlyList<string> elementTypes)
+    {
+        if (elementTypes.Count == 1)
+        {
+            return SyntaxFactory.ParseTypeName(elementTypes[0]);
+        }
+
+        return SyntaxFactory.TupleType(
+            SyntaxFactory.SeparatedList(
+                elementTypes.Select(t =>
+                    SyntaxFactory.TupleElement(SyntaxFactory.ParseTypeName(t)))));
+    }
+
+    /// <summary>
+    /// Converts a complex initializer expression { val1, val2 } to a tuple expression (val1, val2).
+    /// For simple expressions (single-value), returns the expression unchanged.
+    /// </summary>
+    private static ExpressionSyntax ConvertToTupleExpression(ExpressionSyntax expression)
+    {
+        if (expression is not InitializerExpressionSyntax initializer
+            || !initializer.IsKind(SyntaxKind.ComplexElementInitializerExpression))
+        {
+            return expression;
+        }
+
+        var arguments = initializer.Expressions.Select(
+            expr => SyntaxFactory.Argument(expr.WithoutLeadingTrivia().WithoutTrailingTrivia()));
+
+        var tupleExpression = SyntaxFactory.TupleExpression(
+            SyntaxFactory.SeparatedList(arguments))
+            .WithLeadingTrivia(initializer.GetLeadingTrivia())
+            .WithTrailingTrivia(initializer.GetTrailingTrivia());
+
+        return tupleExpression;
+    }
+
     private CompilationUnitSyntax TransformAssertions(CompilationUnitSyntax root)
     {
         var currentRoot = root;
diff --git a/TUnit.Analyzers.CodeFixers/TwoPhase/XUnitTwoPhaseAnalyzer.cs b/TUnit.Analyzers.CodeFixers/TwoPhase/XUnitTwoPhaseAnalyzer.cs
index 9a13310ca0..68c50ac78b 100644
--- a/TUnit.Analyzers.CodeFixers/TwoPhase/XUnitTwoPhaseAnalyzer.cs
+++ b/TUnit.Analyzers.CodeFixers/TwoPhase/XUnitTwoPhaseAnalyzer.cs
@@ -1833,11 +1833,11 @@ protected override CompilationUnitSyntax AnalyzeTheoryData(CompilationUnitSyntax
         {
             try
             {
-                // Get the type argument
-                var typeArg = originalGeneric.TypeArgumentList.Arguments.FirstOrDefault();
-                if (typeArg == null) continue;
+                // Get the type arguments
+                var typeArgs = originalGeneric.TypeArgumentList.Arguments;
+                if (typeArgs.Count == 0) continue;
 
-                var elementType = typeArg.ToString();
+                var elementTypes = typeArgs.Select(t => t.ToString()).ToList();
 
                 // Create annotations for both the type and the object creation
                 var typeAnnotation = new SyntaxAnnotation("TUnitMigration", Guid.NewGuid().ToString());
@@ -1845,7 +1845,7 @@ protected override CompilationUnitSyntax AnalyzeTheoryData(CompilationUnitSyntax
 
                 var conversion = new TheoryDataConversion
                 {
-                    ElementType = elementType,
+                    ElementTypes = elementTypes,
                     TypeAnnotation = typeAnnotation,
                     CreationAnnotation = creationAnnotation,
                     OriginalText = originalGeneric.ToString()
diff --git a/TUnit.Analyzers.Tests/XUnitMigrationAnalyzerTests.cs b/TUnit.Analyzers.Tests/XUnitMigrationAnalyzerTests.cs
index dcd7d31399..7b6a603d63 100644
--- a/TUnit.Analyzers.Tests/XUnitMigrationAnalyzerTests.cs
+++ b/TUnit.Analyzers.Tests/XUnitMigrationAnalyzerTests.cs
@@ -563,6 +563,148 @@ public class MyClass
             );
     }
 
+    [Test]
+    public async Task TheoryData_MultiType_Is_Flagged()
+    {
+        await Verifier
+            .VerifyAnalyzerAsync(
+                """
+                {|#0:using System;
+
+                public class MyClass
+                {
+                    public static TheoryData<string, int> MyData
+                    {
+                        get
+                        {
+                            var data = new TheoryData<string, int>
+                            {
+                                { "a", 1 },
+                                { "b", 2 }
+                            };
+                            return data;
+                        }
+                    }
+                }|}
+                """,
+                ConfigureXUnitTest,
+                Verifier.Diagnostic(Rules.XunitMigration).WithLocation(0)
+            );
+    }
+
+    [Test]
+    public async Task TheoryData_MultiType_Can_Be_Converted()
+    {
+        await CodeFixer
+            .VerifyCodeFixAsync(
+                """
+                {|#0:using Xunit;
+
+                public class MyClass
+                {
+                    public static readonly TheoryData<string, int> Items = new()
+                    {
+                        { "a", 1 },
+                        { "b", 2 }
+                    };
+                }|}
+                """,
+                Verifier.Diagnostic(Rules.XunitMigration).WithLocation(0),
+                """
+
+                public class MyClass
+                {
+                    public static readonly IEnumerable<(string, int)> Items = new (string, int)[]
+                    {
+                        ("a", 1),
+                        ("b", 2)
+                    };
+                }
+                """,
+                ConfigureXUnitTest
+            );
+    }
+
+    [Test]
+    public async Task TheoryData_MultiType_PropertyGetter_Can_Be_Converted()
+    {
+        await CodeFixer
+            .VerifyCodeFixAsync(
+                """
+                {|#0:using Xunit;
+
+                public class MyClass
+                {
+                    public static TheoryData<string, int> MyData
+                    {
+                        get
+                        {
+                            var data = new TheoryData<string, int>
+                            {
+                                { "a", 1 },
+                                { "b", 2 }
+                            };
+                            return data;
+                        }
+                    }
+                }|}
+                """,
+                Verifier.Diagnostic(Rules.XunitMigration).WithLocation(0),
+                """
+
+                public class MyClass
+                {
+                    public static IEnumerable<(string, int)> MyData
+                    {
+                        get
+                        {
+                            var data = new (string, int)[]
+                            {
+                                ("a", 1),
+                                ("b", 2)
+                            };
+                            return data;
+                        }
+                    }
+                }
+                """,
+                ConfigureXUnitTest
+            );
+    }
+
+    [Test]
+    public async Task TheoryData_ThreeTypes_Can_Be_Converted()
+    {
+        await CodeFixer
+            .VerifyCodeFixAsync(
+                """
+                {|#0:using Xunit;
+
+                public class MyClass
+                {
+                    public static readonly TheoryData<string, int, bool> Items = new()
+                    {
+                        { "a", 1, true },
+                        { "b", 2, false }
+                    };
+                }|}
+                """,
+                Verifier.Diagnostic(Rules.XunitMigration).WithLocation(0),
+                """
+
+                public class MyClass
+                {
+                    public static readonly IEnumerable<(string, int, bool)> Items = new (string, int, bool)[]
+                    {
+                        ("a", 1, true),
+                        ("b", 2, false)
+                    };
+                }
+                """,
+                ConfigureXUnitTest
+            );
+    }
+
     [Test]
     public async Task ITestOutputHelper_Is_Flagged()
     {