diff --git a/PolyShim.Tests/NetCore21/BinaryReaderTests.cs b/PolyShim.Tests/NetCore21/BinaryReaderTests.cs
new file mode 100644
index 0000000..d983ff6
--- /dev/null
+++ b/PolyShim.Tests/NetCore21/BinaryReaderTests.cs
@@ -0,0 +1,56 @@
+using System;
+using System.Buffers;
+using System.IO;
+using FluentAssertions;
+using Xunit;
+
+namespace PolyShim.Tests.NetCore21;
+
+public class BinaryReaderTests
+{
+    [Fact]
+    public void Read_ByteSpan_Test()
+    {
+        // Arrange
+        using var stream = new MemoryStream([1, 2, 3, 4, 5]);
+        using var reader = new BinaryReader(stream);
+        var buffer = ArrayPool<byte>.Shared.Rent((int)stream.Length);
+
+        try
+        {
+            // Act
+            var bytesRead = reader.Read(buffer.AsSpan(0, (int)stream.Length));
+
+            // Assert
+            bytesRead.Should().Be(5);
+            buffer.Should().StartWith([1, 2, 3, 4, 5]);
+        }
+        finally
+        {
+            ArrayPool<byte>.Shared.Return(buffer);
+        }
+    }
+
+    [Fact]
+    public void Read_CharSpan_Test()
+    {
+        // Arrange
+        using var stream = new MemoryStream("Hello"u8.ToArray());
+        using var reader = new BinaryReader(stream);
+        var buffer = ArrayPool<char>.Shared.Rent(5);
+
+        try
+        {
+            // Act
+            var charsRead = reader.Read(buffer.AsSpan(0, 5));
+
+            // Assert
+            charsRead.Should().Be(5);
+            buffer.Should().StartWith("Hello");
+        }
+        finally
+        {
+            ArrayPool<char>.Shared.Return(buffer);
+        }
+    }
+}
diff --git a/PolyShim.Tests/NetCore21/BinaryWriterTests.cs b/PolyShim.Tests/NetCore21/BinaryWriterTests.cs
new file mode 100644
index 0000000..4f75a1f
--- /dev/null
+++ b/PolyShim.Tests/NetCore21/BinaryWriterTests.cs
@@ -0,0 +1,66 @@
+using System;
+using System.Buffers;
+using System.IO;
+using FluentAssertions;
+using Xunit;
+
+namespace PolyShim.Tests.NetCore21;
+
+public class BinaryWriterTests
+{
+    [Fact]
+    public void Write_ByteSpan_Test()
+    {
+        // Arrange
+        using var stream = new MemoryStream();
+        using var writer = new BinaryWriter(stream);
+        var buffer = ArrayPool<byte>.Shared.Rent(5);
+
+        buffer[0] = 1;
+        buffer[1] = 2;
+        buffer[2] = 3;
+        buffer[3] = 4;
+        buffer[4] = 5;
+
+        try
+        {
+            // Act
+            writer.Write(buffer.AsSpan(0, 5));
+
+            // Assert
+            stream.ToArray().Should().Equal([1, 2, 3, 4, 5]);
+        }
+        finally
+        {
+            ArrayPool<byte>.Shared.Return(buffer);
+        }
+    }
+
+    [Fact]
+    public void Write_CharSpan_Test()
+    {
+        // Arrange
+        using var stream = new MemoryStream();
+        using var writer = new BinaryWriter(stream);
+        var buffer = ArrayPool<char>.Shared.Rent(5);
+
+        buffer[0] = 'H';
+        buffer[1] = 'e';
+        buffer[2] = 'l';
+        buffer[3] = 'l';
+        buffer[4] = 'o';
+
+        try
+        {
+            // Act
+            writer.Write(buffer.AsSpan(0, 5));
+
+            // Assert
+            stream.ToArray().Should().Equal("Hello"u8.ToArray());
+        }
+        finally
+        {
+            ArrayPool<char>.Shared.Return(buffer);
+        }
+    }
+}
diff --git a/PolyShim/NetCore21/BinaryReader.cs b/PolyShim/NetCore21/BinaryReader.cs
new file mode 100644
index 0000000..9d295d1
--- /dev/null
+++ b/PolyShim/NetCore21/BinaryReader.cs
@@ -0,0 +1,37 @@
+#if (NETCOREAPP && !NETCOREAPP2_1_OR_GREATER) || (NETFRAMEWORK) || (NETSTANDARD && !NETSTANDARD2_1_OR_GREATER)
+#nullable enable
+#pragma warning disable CS0436
+
+using System;
+using System.IO;
+using System.Diagnostics.CodeAnalysis;
+
+#if !POLYSHIM_INCLUDE_COVERAGE
+[ExcludeFromCodeCoverage]
+#endif
+internal static class MemberPolyfills_NetCore21_BinaryReader
+{
+    extension(BinaryReader reader)
+    {
+        // https://learn.microsoft.com/dotnet/api/system.io.binaryreader.read#system-io-binaryreader-read(system-span((system-byte)))
+        public int Read(Span<byte> buffer)
+        {
+            var bufferArray = new byte[buffer.Length];
+            var result = reader.Read(bufferArray, 0, bufferArray.Length);
+            bufferArray.AsSpan(0, result).CopyTo(buffer);
+
+            return result;
+        }
+
+        // https://learn.microsoft.com/dotnet/api/system.io.binaryreader.read#system-io-binaryreader-read(system-span((system-char)))
+        public int Read(Span<char> buffer)
+        {
+            var bufferArray = new char[buffer.Length];
+            var result = reader.Read(bufferArray, 0, bufferArray.Length);
+            bufferArray.AsSpan(0, result).CopyTo(buffer);
+
+            return result;
+        }
+    }
+}
+#endif
diff --git a/PolyShim/NetCore21/BinaryWriter.cs b/PolyShim/NetCore21/BinaryWriter.cs
new file mode 100644
index 0000000..a3adf8c
--- /dev/null
+++ b/PolyShim/NetCore21/BinaryWriter.cs
@@ -0,0 +1,31 @@
+#if (NETCOREAPP && !NETCOREAPP2_1_OR_GREATER) || (NETFRAMEWORK) || (NETSTANDARD && !NETSTANDARD2_1_OR_GREATER)
+#nullable enable
+#pragma warning disable CS0436
+
+using System;
+using System.IO;
+using System.Diagnostics.CodeAnalysis;
+
+#if !POLYSHIM_INCLUDE_COVERAGE
+[ExcludeFromCodeCoverage]
+#endif
+internal static class MemberPolyfills_NetCore21_BinaryWriter
+{
+    extension(BinaryWriter writer)
+    {
+        // https://learn.microsoft.com/dotnet/api/system.io.binarywriter.write#system-io-binarywriter-write(system-readonlyspan((system-byte)))
+        public void Write(ReadOnlySpan<byte> buffer)
+        {
+            var bufferArray = buffer.ToArray();
+            writer.Write(bufferArray, 0, bufferArray.Length);
+        }
+
+        // https://learn.microsoft.com/dotnet/api/system.io.binarywriter.write#system-io-binarywriter-write(system-readonlyspan((system-char)))
+        public void Write(ReadOnlySpan<char> buffer)
+        {
+            var bufferArray = buffer.ToArray();
+            writer.Write(bufferArray, 0, bufferArray.Length);
+        }
+    }
+}
+#endif
diff --git a/Signatures.md b/Signatures.md
index 49bc126..581cd83 100644
--- a/Signatures.md
+++ b/Signatures.md
@@ -1,8 +1,8 @@
 # Signatures
 
-- **Total:** 541
+- **Total:** 545
 - **Types:** 113
-- **Members:** 428
+- **Members:** 432
 
 ___
 
@@ -45,6 +45,12 @@ ___
   - [**[struct]**](https://learn.microsoft.com/dotnet/api/system.runtime.compilerservices.asyncvaluetaskmethodbuilder) <sup><sub>.NET Core 2.1</sub></sup>
 - `AsyncValueTaskMethodBuilder<TResult>`
   - [**[struct]**](https://learn.microsoft.com/dotnet/api/system.runtime.compilerservices.asyncvaluetaskmethodbuilder-1) <sup><sub>.NET Core 2.1</sub></sup>
+- `BinaryReader`
+  - [`int Read(Span<byte>)`](https://learn.microsoft.com/dotnet/api/system.io.binaryreader.read#system-io-binaryreader-read(system-span((system-byte)))) <sup><sub>.NET Core 2.1</sub></sup>
+  - [`int Read(Span<char>)`](https://learn.microsoft.com/dotnet/api/system.io.binaryreader.read#system-io-binaryreader-read(system-span((system-char)))) <sup><sub>.NET Core 2.1</sub></sup>
+- `BinaryWriter`
+  - [`void Write(ReadOnlySpan<byte>)`](https://learn.microsoft.com/dotnet/api/system.io.binarywriter.write#system-io-binarywriter-write(system-readonlyspan((system-byte)))) <sup><sub>.NET Core 2.1</sub></sup>
+  - [`void Write(ReadOnlySpan<char>)`](https://learn.microsoft.com/dotnet/api/system.io.binarywriter.write#system-io-binarywriter-write(system-readonlyspan((system-char)))) <sup><sub>.NET Core 2.1</sub></sup>
 - `byte`
   - [`static bool TryParse(ReadOnlySpan<char>, IFormatProvider?, out byte)`](https://learn.microsoft.com/dotnet/api/system.byte.tryparse#system-byte-tryparse(system-readonlyspan((system-char))-system-iformatprovider-system-byte@)) <sup><sub>.NET 7.0</sub></sup>
   - [`static bool TryParse(string?, IFormatProvider?, out byte)`](https://learn.microsoft.com/dotnet/api/system.byte.tryparse#system-byte-tryparse(system-string-system-iformatprovider-system-byte@)) <sup><sub>.NET 7.0</sub></sup>