diff --git a/src/Authentication/Authentication.Test/Helpers/PSObjectJsonConverterTests.cs b/src/Authentication/Authentication.Test/Helpers/PSObjectJsonConverterTests.cs
new file mode 100644
index 00000000000..3baba24318e
--- /dev/null
+++ b/src/Authentication/Authentication.Test/Helpers/PSObjectJsonConverterTests.cs
@@ -0,0 +1,148 @@
+using System.Collections;
+using System.Management.Automation;
+using System.Net.Http;
+
+using Microsoft.Graph.PowerShell.Authentication.Cmdlets;
+using Microsoft.Graph.PowerShell.Authentication.Helpers;
+
+using Newtonsoft.Json;
+using Newtonsoft.Json.Linq;
+
+using Xunit;
+
+namespace Microsoft.Graph.Authentication.Test.Helpers
+{
+    public class PSObjectJsonConverterTests
+    {
+        [Fact]
+        public void ShouldSerializePSObjectWrappedStringAsPlainString()
+        {
+            // Mimics a value produced by the PowerShell pipeline, e.g. bare $_ in ForEach-Object.
+            // See https://github.com/microsoftgraph/msgraph-sdk-powershell/issues/3654.
+            var body = new Hashtable
+            {
+                {
+                    "message", new Hashtable
+                    {
+                        {
+                            "toRecipients", new object[]
+                            {
+                                new Hashtable
+                                {
+                                    {
+                                        "emailAddress", new Hashtable
+                                        {
+                                            { "address", PSObject.AsPSObject("recipient@example.com") }
+                                        }
+                                    }
+                                }
+                            }
+                        }
+                    }
+                },
+                { "saveToSentItems", true }
+            };
+
+            var json = JsonConvert.SerializeObject(body, new PSObjectJsonConverter());
+
+            var parsedBody = JObject.Parse(json);
+            Assert.Equal("recipient@example.com",
+                parsedBody.SelectToken("message.toRecipients[0].emailAddress.address").Value<string>());
+            Assert.True(parsedBody.SelectToken("saveToSentItems").Value<bool>());
+        }
+
+        [Fact]
+        public void ShouldSerializePSObjectWrappedPrimitivesAsUnderlyingValues()
+        {
+            var body = new Hashtable
+            {
+                { "count", PSObject.AsPSObject(42) },
+                { "enabled", PSObject.AsPSObject(true) }
+            };
+
+            var json = JsonConvert.SerializeObject(body, new PSObjectJsonConverter());
+
+            var parsedBody = JObject.Parse(json);
+            Assert.Equal(42, parsedBody.SelectToken("count").Value<int>());
+            Assert.True(parsedBody.SelectToken("enabled").Value<bool>());
+        }
+
+        [Fact]
+        public void ShouldSerializePSObjectWrappedDictionary()
+        {
+            var body = new Hashtable
+            {
+                {
+                    "emailAddress", PSObject.AsPSObject(new Hashtable
+                    {
+                        { "address", PSObject.AsPSObject("recipient@example.com") }
+                    })
+                }
+            };
+
+            var json = JsonConvert.SerializeObject(body, new PSObjectJsonConverter());
+
+            var parsedBody = JObject.Parse(json);
+            Assert.Equal("recipient@example.com",
+                parsedBody.SelectToken("emailAddress.address").Value<string>());
+        }
+
+        [Fact]
+        public void ShouldSerializePSCustomObjectAsJsonObject()
+        {
+            var emailAddress = new PSObject();
+            emailAddress.Properties.Add(new PSNoteProperty("address", PSObject.AsPSObject("recipient@example.com")));
+            var body = new Hashtable
+            {
+                { "emailAddress", emailAddress }
+            };
+
+            var json = JsonConvert.SerializeObject(body, new PSObjectJsonConverter());
+
+            var parsedBody = JObject.Parse(json);
+            Assert.Equal("recipient@example.com",
+                parsedBody.SelectToken("emailAddress.address").Value<string>());
+        }
+
+        [Fact]
+        public void SetRequestContentShouldSerializeDictionaryWithPSObjectWrappedValues()
+        {
+            var cmdlet = new InvokeMgGraphRequest();
+            using (var request = new HttpRequestMessage(HttpMethod.Post,
+                "https://graph.microsoft.com/v1.0/users/sender@example.com/sendMail"))
+            {
+                var body = new Hashtable
+                {
+                    {
+                        "message", new Hashtable
+                        {
+                            {
+                                "toRecipients", new object[]
+                                {
+                                    new Hashtable
+                                    {
+                                        {
+                                            "emailAddress", new Hashtable
+                                            {
+                                                { "address", PSObject.AsPSObject("recipient@example.com") }
+                                            }
+                                        }
+                                    }
+                                }
+                            }
+                        }
+                    },
+                    { "saveToSentItems", true }
+                };
+
+                var contentLength = cmdlet.SetRequestContent(request, body);
+
+                Assert.True(contentLength > 0);
+                var json = request.Content.ReadAsStringAsync().GetAwaiter().GetResult();
+                var parsedBody = JObject.Parse(json);
+                Assert.Equal("recipient@example.com",
+                    parsedBody.SelectToken("message.toRecipients[0].emailAddress.address").Value<string>());
+            }
+        }
+    }
+}
diff --git a/src/Authentication/Authentication.Test/Microsoft.Graph.Authentication.Test.csproj b/src/Authentication/Authentication.Test/Microsoft.Graph.Authentication.Test.csproj
index ccaa28e8fb4..2dda94b996d 100644
--- a/src/Authentication/Authentication.Test/Microsoft.Graph.Authentication.Test.csproj
+++ b/src/Authentication/Authentication.Test/Microsoft.Graph.Authentication.Test.csproj
@@ -7,7 +7,11 @@
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.6.2" />
     <!-- As described in this post https://devblogs.microsoft.com/powershell/depending-on-the-right-powershell-nuget-package-in-your-net-project, reference the SDK for dotnetcore-->
-    <PackageReference Include="Microsoft.PowerShell.SDK" Version="7.5.0" PrivateAssets="all" Condition="'$(TargetFramework)' == 'net8.0'" />
+    <!-- Microsoft.PowerShell.SDK 7.5.x targets net9.0 and contributes no assemblies to a net8.0 build,
+         which silently leaves the PowerShellStandard.Library stub (whose APIs return null) as the runtime
+         System.Management.Automation. Keep this on the latest 7.4.x (net8.0) release so PSObject-dependent
+         tests exercise the real PowerShell runtime. -->
+    <PackageReference Include="Microsoft.PowerShell.SDK" Version="7.4.17" PrivateAssets="all" Condition="'$(TargetFramework)' == 'net8.0'" />
     <PackageReference Include="Moq" Version="4.20.70" />
   <PackageReference Include="System.Net.Http" Version="4.3.4" />
     <PackageReference Include="xunit" Version="2.4.2" />
diff --git a/src/Authentication/Authentication/Cmdlets/InvokeMgGraphRequest.cs b/src/Authentication/Authentication/Cmdlets/InvokeMgGraphRequest.cs
index 4e16b462486..b93e309f3dd 100644
--- a/src/Authentication/Authentication/Cmdlets/InvokeMgGraphRequest.cs
+++ b/src/Authentication/Authentication/Cmdlets/InvokeMgGraphRequest.cs
@@ -567,7 +567,7 @@ private async Task<HttpResponseMessage> GetResponseAsync(HttpClient client, Http
         /// <param name="request"></param>
         /// <param name="content"></param>
         /// <returns></returns>
-        private long SetRequestContent(HttpRequestMessage request, IDictionary content)
+        internal long SetRequestContent(HttpRequestMessage request, IDictionary content)
         {
             if (request == null)
             {
@@ -579,8 +579,10 @@ private long SetRequestContent(HttpRequestMessage request, IDictionary content)
                 throw new ArgumentNullException(nameof(content));
             }
 
-            // Covert all dictionaries to Json
-            var body = JsonConvert.SerializeObject(content);
+            // Convert all dictionaries to Json.
+            // Unwrap PSObject-wrapped values (e.g. values produced by the PowerShell pipeline) so the
+            // underlying CLR values are serialized instead of their PSObject wrappers. See https://github.com/microsoftgraph/msgraph-sdk-powershell/issues/3654.
+            var body = JsonConvert.SerializeObject(content, new PSObjectJsonConverter());
             return SetRequestContent(request, body);
         }
 
diff --git a/src/Authentication/Authentication/Helpers/PSObjectJsonConverter.cs b/src/Authentication/Authentication/Helpers/PSObjectJsonConverter.cs
new file mode 100644
index 00000000000..a472d94f364
--- /dev/null
+++ b/src/Authentication/Authentication/Helpers/PSObjectJsonConverter.cs
@@ -0,0 +1,56 @@
+// ------------------------------------------------------------------------------
+//  Copyright (c) Microsoft Corporation.  All Rights Reserved.  Licensed under the MIT License.  See License in the project root for license information.
+// ------------------------------------------------------------------------------
+
+using Newtonsoft.Json;
+using System;
+using System.Management.Automation;
+
+namespace Microsoft.Graph.PowerShell.Authentication.Helpers
+{
+    /// <summary>
+    ///     Serializes <see cref="PSObject" /> values by unwrapping them to their underlying base object.
+    ///     PowerShell wraps values that pass through the pipeline (e.g. bare $_ in ForEach-Object) in a
+    ///     <see cref="PSObject" />. Without this converter, Newtonsoft.Json reflects over the PowerShell
+    ///     adapted members of the wrapper (such as the Chars indexed property on strings) instead of the
+    ///     underlying value and fails with a self-referencing loop error.
+    /// </summary>
+    internal class PSObjectJsonConverter : JsonConverter
+    {
+        public override bool CanRead => false;
+
+        public override bool CanConvert(Type objectType)
+        {
+            return typeof(PSObject).IsAssignableFrom(objectType);
+        }
+
+        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
+        {
+            var psObject = (PSObject)value;
+            if (psObject.BaseObject is PSCustomObject)
+            {
+                // Pure custom objects (e.g. [pscustomobject]@{ ... }) have no underlying CLR object
+                // to fall back on; project their properties into a JSON object instead.
+                writer.WriteStartObject();
+                foreach (var property in psObject.Properties)
+                {
+                    writer.WritePropertyName(property.Name);
+                    serializer.Serialize(writer, property.Value);
+                }
+                writer.WriteEndObject();
+            }
+            else
+            {
+                // Serialize the underlying CLR object. Nested PSObject-wrapped values (e.g. inside
+                // dictionaries or collections) are routed back through this converter by the serializer.
+                serializer.Serialize(writer, psObject.BaseObject);
+            }
+        }
+
+        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
+        {
+            throw new NotSupportedException();
+        }
+    }
+}
+