diff --git a/NGitLab.Mock.Tests/ProjectsMockTests.cs b/NGitLab.Mock.Tests/ProjectsMockTests.cs
index 404e8f66..ca142791 100644
--- a/NGitLab.Mock.Tests/ProjectsMockTests.cs
+++ b/NGitLab.Mock.Tests/ProjectsMockTests.cs
@@ -47,6 +47,45 @@ public void Test_projects_created_can_be_found()
         Assert.That(project.Namespace.FullPath, Is.EqualTo("testgroup"));
     }
 
+    [Test]
+    public void GetProjectAsync_WhenProjectDoesNotExist_ShouldThrowNotFound()
+    {
+        // Arrange
+        using var server = new GitLabConfig()
+            .WithUser("TestUser", isDefault: true)
+            .BuildServer();
+        var gitLabClient = server.CreateClient();
+        var projectClient = gitLabClient.Projects;
+
+        // Act/Assert
+        var ex = Assert.ThrowsAsync<GitLabException>(() => projectClient.GetAsync("baz1234"));
+
+        Assert.That(ex.StatusCode, Is.EqualTo(HttpStatusCode.NotFound));
+    }
+
+    [Test]
+    public void GetProjectAsync_WhenProjectInaccessible_ShouldThrowNotFound()
+    {
+        // Arrange
+        using var server = new GitLabConfig()
+            .WithUser("TestUser1", isDefault: true)
+            .WithUser("TestUser2")
+            .BuildServer();
+        var testUser1ProjectClient = server.CreateClient("TestUser1").Projects;
+        var testUser2ProjectClient = server.CreateClient("TestUser2").Projects;
+
+        var testUser2Project = testUser2ProjectClient.Create(new ProjectCreate
+        {
+            Name = $"Project_Test_{Guid.NewGuid()}",
+            VisibilityLevel = VisibilityLevel.Private,
+        });
+
+        // Act/Assert
+        var ex = Assert.ThrowsAsync<GitLabException>(() => testUser1ProjectClient.GetAsync(testUser2Project.Id));
+
+        Assert.That(ex.StatusCode, Is.EqualTo(HttpStatusCode.NotFound));
+    }
+
     [Test]
     public void Test_project_can_be_cloned_by_default()
     {
diff --git a/NGitLab.Mock/Clients/ClientBase.cs b/NGitLab.Mock/Clients/ClientBase.cs
index 4ed64347..ab562f0c 100644
--- a/NGitLab.Mock/Clients/ClientBase.cs
+++ b/NGitLab.Mock/Clients/ClientBase.cs
@@ -85,8 +85,15 @@ protected Project GetProject(object id, ProjectPermission permissions)
             _ => throw new ArgumentException($"Id of type '{id.GetType()}' is not supported"),
         };
 
-        if (project == null || !project.CanUserViewProject(Context.User))
-            throw new GitLabNotFoundException("Project does not exist or User doesn't have permission to view it");
+        if (project is null || !project.CanUserViewProject(Context.User))
+        {
+            throw new GitLabException("GitLab server returned an error (NotFound): 404 Project Not Found.")
+            {
+                MethodType = Impl.MethodType.Get,
+                StatusCode = HttpStatusCode.NotFound,
+                ErrorMessage = "404 Project Not Found",
+            };
+        }
 
         switch (permissions)
         {
diff --git a/NGitLab.Tests/ProjectsTests.cs b/NGitLab.Tests/ProjectsTests.cs
index fcfda9ad..a28c798c 100644
--- a/NGitLab.Tests/ProjectsTests.cs
+++ b/NGitLab.Tests/ProjectsTests.cs
@@ -87,6 +87,27 @@ public async Task GetProjectAsync_WhenProjectDoesNotExist_ShouldThrowNotFound()
         Assert.That(ex.StatusCode, Is.EqualTo(HttpStatusCode.NotFound));
     }
 
+    [Test]
+    [NGitLabRetry]
+    public async Task GetProjectAsync_WhenProjectInaccessible_ShouldThrowNotFound()
+    {
+        // Arrange
+        using var context = await GitLabTestContext.CreateAsync();
+        var adminProjectClient = context.AdminClient.Projects;
+        var userProjectClient = context.Client.Projects;
+
+        var adminProject = adminProjectClient.Create(new ProjectCreate
+        {
+            Name = "Project_Test_" + context.GetRandomNumber().ToStringInvariant(),
+            VisibilityLevel = VisibilityLevel.Private,
+        });
+
+        // Act/Assert
+        var ex = Assert.ThrowsAsync<GitLabException>(() => userProjectClient.GetAsync(adminProject.Id));
+
+        Assert.That(ex.StatusCode, Is.EqualTo(HttpStatusCode.NotFound));
+    }
+
     [Test]
     [NGitLabRetry]
     public async Task GetProjectsAsync()