diff --git a/src/CodingWithCalvin.ProjectRenamifier/Commands/RenamifyProjectCommand.cs b/src/CodingWithCalvin.ProjectRenamifier/Commands/RenamifyProjectCommand.cs
index e8ea9e6..9d02678 100644
--- a/src/CodingWithCalvin.ProjectRenamifier/Commands/RenamifyProjectCommand.cs
+++ b/src/CodingWithCalvin.ProjectRenamifier/Commands/RenamifyProjectCommand.cs
@@ -161,6 +161,12 @@ private void RenameProject(Project project, DTE2 dte)
                     SourceFileService.UpdateUsingStatementsInSolution(dte.Solution, currentName, newName);
                 });
 
+                // Step 11: Update fully qualified type references across the solution
+                ExecuteStep(progressDialog, stepIndex++, () =>
+                {
+                    SourceFileService.UpdateFullyQualifiedReferencesInSolution(dte.Solution, currentName, newName);
+                });
+
                 // Mark as complete and close after a brief delay
                 progressDialog.Complete();
                 DoEvents();
diff --git a/src/CodingWithCalvin.ProjectRenamifier/Dialogs/RenameProgressDialog.xaml b/src/CodingWithCalvin.ProjectRenamifier/Dialogs/RenameProgressDialog.xaml
index 7c94dc3..cfffd5b 100644
--- a/src/CodingWithCalvin.ProjectRenamifier/Dialogs/RenameProgressDialog.xaml
+++ b/src/CodingWithCalvin.ProjectRenamifier/Dialogs/RenameProgressDialog.xaml
@@ -3,7 +3,7 @@
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         Title="Renaming Project"
         Width="400"
-        Height="340"
+        Height="360"
         ResizeMode="NoResize"
         WindowStartupLocation="CenterOwner"
         ShowInTaskbar="False">
diff --git a/src/CodingWithCalvin.ProjectRenamifier/Dialogs/RenameProgressDialog.xaml.cs b/src/CodingWithCalvin.ProjectRenamifier/Dialogs/RenameProgressDialog.xaml.cs
index 3613c3e..e0e561a 100644
--- a/src/CodingWithCalvin.ProjectRenamifier/Dialogs/RenameProgressDialog.xaml.cs
+++ b/src/CodingWithCalvin.ProjectRenamifier/Dialogs/RenameProgressDialog.xaml.cs
@@ -26,7 +26,8 @@ public RenameProgressDialog(string projectName)
                 new ProgressStep("Renaming project directory"),
                 new ProgressStep("Updating project references"),
                 new ProgressStep("Re-adding project to solution"),
-                new ProgressStep("Updating using statements")
+                new ProgressStep("Updating using statements"),
+                new ProgressStep("Updating fully qualified references")
             };
 
             StepsList.ItemsSource = Steps;
diff --git a/src/CodingWithCalvin.ProjectRenamifier/Services/SourceFileService.cs b/src/CodingWithCalvin.ProjectRenamifier/Services/SourceFileService.cs
index bfcd099..7828ef0 100644
--- a/src/CodingWithCalvin.ProjectRenamifier/Services/SourceFileService.cs
+++ b/src/CodingWithCalvin.ProjectRenamifier/Services/SourceFileService.cs
@@ -10,6 +10,115 @@ namespace CodingWithCalvin.ProjectRenamifier.Services
     /// </summary>
     internal static class SourceFileService
     {
+        /// <summary>
+        /// Updates fully qualified type references in all .cs files across the entire solution.
+        /// For example: OldName.MyClass → NewName.MyClass
+        /// </summary>
+        /// <param name="solution">The solution to scan.</param>
+        /// <param name="oldNamespace">The old namespace to find.</param>
+        /// <param name="newNamespace">The new namespace to replace with.</param>
+        /// <returns>The number of files modified.</returns>
+        public static int UpdateFullyQualifiedReferencesInSolution(Solution solution, string oldNamespace, string newNamespace)
+        {
+            ThreadHelper.ThrowIfNotOnUIThread();
+
+            var modifiedCount = 0;
+
+            foreach (Project project in solution.Projects)
+            {
+                modifiedCount += UpdateFullyQualifiedReferencesInProjectTree(project, oldNamespace, newNamespace);
+            }
+
+            return modifiedCount;
+        }
+
+        /// <summary>
+        /// Recursively updates fully qualified references in a project (handles solution folders).
+        /// </summary>
+        private static int UpdateFullyQualifiedReferencesInProjectTree(Project project, string oldNamespace, string newNamespace)
+        {
+            ThreadHelper.ThrowIfNotOnUIThread();
+
+            if (project == null)
+            {
+                return 0;
+            }
+
+            // Handle solution folders
+            if (project.Kind == EnvDTE.Constants.vsProjectKindSolutionItems)
+            {
+                var count = 0;
+                foreach (ProjectItem item in project.ProjectItems)
+                {
+                    if (item.SubProject != null)
+                    {
+                        count += UpdateFullyQualifiedReferencesInProjectTree(item.SubProject, oldNamespace, newNamespace);
+                    }
+                }
+                return count;
+            }
+
+            // Process actual project
+            if (!string.IsNullOrEmpty(project.FullName) && File.Exists(project.FullName))
+            {
+                var projectDirectory = Path.GetDirectoryName(project.FullName);
+                if (!string.IsNullOrEmpty(projectDirectory) && Directory.Exists(projectDirectory))
+                {
+                    return UpdateFullyQualifiedReferencesInDirectory(projectDirectory, oldNamespace, newNamespace);
+                }
+            }
+
+            return 0;
+        }
+
+        /// <summary>
+        /// Updates fully qualified references in all .cs files within a directory.
+        /// </summary>
+        private static int UpdateFullyQualifiedReferencesInDirectory(string directory, string oldNamespace, string newNamespace)
+        {
+            var csFiles = Directory.GetFiles(directory, "*.cs", SearchOption.AllDirectories);
+            var modifiedCount = 0;
+
+            foreach (var filePath in csFiles)
+            {
+                if (UpdateFullyQualifiedReferencesInFile(filePath, oldNamespace, newNamespace))
+                {
+                    modifiedCount++;
+                }
+            }
+
+            return modifiedCount;
+        }
+
+        /// <summary>
+        /// Updates fully qualified type references in a single source file.
+        /// Matches patterns like OldName.MyClass, OldName.Sub.Type but not SomeOldName.Type
+        /// </summary>
+        /// <param name="filePath">Full path to the .cs file.</param>
+        /// <param name="oldNamespace">The old namespace to find.</param>
+        /// <param name="newNamespace">The new namespace to replace with.</param>
+        /// <returns>True if the file was modified, false otherwise.</returns>
+        public static bool UpdateFullyQualifiedReferencesInFile(string filePath, string oldNamespace, string newNamespace)
+        {
+            var encoding = DetectEncoding(filePath);
+            var content = File.ReadAllText(filePath, encoding);
+            var originalContent = content;
+
+            // Pattern matches OldName followed by a dot and an identifier
+            // Uses word boundary \b to avoid matching partial names like SomeOldName
+            // Matches: OldName.Class, OldName.Sub.Class, etc.
+            var pattern = $@"\b{Regex.Escape(oldNamespace)}\.";
+            content = Regex.Replace(content, pattern, $"{newNamespace}.");
+
+            if (content != originalContent)
+            {
+                File.WriteAllText(filePath, content, encoding);
+                return true;
+            }
+
+            return false;
+        }
+
         /// <summary>
         /// Updates using statements in all .cs files across the entire solution.
         /// </summary>