diff --git a/src/Api/Controllers/OrganizationUsersController.cs b/src/Api/Controllers/OrganizationUsersController.cs
index d1c4ebacd6..e1a1a3a576 100644
--- a/src/Api/Controllers/OrganizationUsersController.cs
+++ b/src/Api/Controllers/OrganizationUsersController.cs
@@ -1,6 +1,8 @@
 using Bit.Api.Models.Request.Organizations;
 using Bit.Api.Models.Response;
 using Bit.Api.Models.Response.Organizations;
+using Bit.Api.Vault.AuthorizationHandlers.OrganizationUsers;
+using Bit.Core;
 using Bit.Core.Context;
 using Bit.Core.Enums;
 using Bit.Core.Exceptions;
@@ -31,6 +33,10 @@ public class OrganizationUsersController : Controller
     private readonly ICountNewSmSeatsRequiredQuery _countNewSmSeatsRequiredQuery;
     private readonly IUpdateSecretsManagerSubscriptionCommand _updateSecretsManagerSubscriptionCommand;
     private readonly IUpdateOrganizationUserGroupsCommand _updateOrganizationUserGroupsCommand;
+    private readonly IFeatureService _featureService;
+    private readonly IAuthorizationService _authorizationService;
+
+    private bool FlexibleCollectionsIsEnabled => _featureService.IsEnabled(FeatureFlagKeys.FlexibleCollections, _currentContext);
 
     public OrganizationUsersController(
         IOrganizationRepository organizationRepository,
@@ -43,7 +49,9 @@ public class OrganizationUsersController : Controller
         ICurrentContext currentContext,
         ICountNewSmSeatsRequiredQuery countNewSmSeatsRequiredQuery,
         IUpdateSecretsManagerSubscriptionCommand updateSecretsManagerSubscriptionCommand,
-        IUpdateOrganizationUserGroupsCommand updateOrganizationUserGroupsCommand)
+        IUpdateOrganizationUserGroupsCommand updateOrganizationUserGroupsCommand,
+        IFeatureService featureService,
+        IAuthorizationService authorizationService)
     {
         _organizationRepository = organizationRepository;
         _organizationUserRepository = organizationUserRepository;
@@ -56,6 +64,8 @@ public class OrganizationUsersController : Controller
         _countNewSmSeatsRequiredQuery = countNewSmSeatsRequiredQuery;
         _updateSecretsManagerSubscriptionCommand = updateSecretsManagerSubscriptionCommand;
         _updateOrganizationUserGroupsCommand = updateOrganizationUserGroupsCommand;
+        _featureService = featureService;
+        _authorizationService = authorizationService;
     }
 
     [HttpGet("{id}")]
@@ -78,18 +88,20 @@ public class OrganizationUsersController : Controller
     }
 
     [HttpGet("")]
-    public async Task<ListResponseModel<OrganizationUserUserDetailsResponseModel>> Get(string orgId, bool includeGroups = false, bool includeCollections = false)
+    public async Task<ListResponseModel<OrganizationUserUserDetailsResponseModel>> Get(Guid orgId, bool includeGroups = false, bool includeCollections = false)
     {
-        var orgGuidId = new Guid(orgId);
-        if (!await _currentContext.ViewAllCollections(orgGuidId) &&
-            !await _currentContext.ViewAssignedCollections(orgGuidId) &&
-            !await _currentContext.ManageGroups(orgGuidId) &&
-            !await _currentContext.ManageUsers(orgGuidId))
+        var authorized = FlexibleCollectionsIsEnabled ?
+            (await _authorizationService.AuthorizeAsync(User, orgId, OrganizationUserOperations.Read(orgId))).Succeeded :
+            await _currentContext.ViewAllCollections(orgId) ||
+            await _currentContext.ViewAssignedCollections(orgId) ||
+            await _currentContext.ManageGroups(orgId) ||
+            await _currentContext.ManageUsers(orgId);
+        if (!authorized)
         {
             throw new NotFoundException();
         }
 
-        var organizationUsers = await _organizationUserRepository.GetManyDetailsByOrganizationAsync(orgGuidId, includeGroups, includeCollections);
+        var organizationUsers = await _organizationUserRepository.GetManyDetailsByOrganizationAsync(orgId, includeGroups, includeCollections);
         var responseTasks = organizationUsers.Select(async o => new OrganizationUserUserDetailsResponseModel(o,
             await _userService.TwoFactorIsEnabledAsync(o)));
         var responses = await Task.WhenAll(responseTasks);
diff --git a/src/Api/Vault/AuthorizationHandlers/OrganizationUsers/OrganizationUserAuthorizationHandler.cs b/src/Api/Vault/AuthorizationHandlers/OrganizationUsers/OrganizationUserAuthorizationHandler.cs
new file mode 100644
index 0000000000..27614a062e
--- /dev/null
+++ b/src/Api/Vault/AuthorizationHandlers/OrganizationUsers/OrganizationUserAuthorizationHandler.cs
@@ -0,0 +1,76 @@
+using Bit.Core;
+using Bit.Core.Context;
+using Bit.Core.Enums;
+using Bit.Core.Exceptions;
+using Bit.Core.Services;
+using Microsoft.AspNetCore.Authorization;
+
+namespace Bit.Api.Vault.AuthorizationHandlers.OrganizationUsers;
+
+/// <summary>
+/// Handles authorization logic for OrganizationUser objects.
+/// This uses new logic implemented in the Flexible Collections initiative.
+/// </summary>
+public class OrganizationUserAuthorizationHandler : AuthorizationHandler<OrganizationUserOperationRequirement>
+{
+    private readonly ICurrentContext _currentContext;
+    private readonly IFeatureService _featureService;
+
+    public OrganizationUserAuthorizationHandler(
+        ICurrentContext currentContext,
+        IFeatureService featureService)
+    {
+        _currentContext = currentContext;
+        _featureService = featureService;
+    }
+
+    protected override async Task HandleRequirementAsync(AuthorizationHandlerContext context,
+        OrganizationUserOperationRequirement requirement)
+    {
+        if (!_featureService.IsEnabled(FeatureFlagKeys.FlexibleCollections, _currentContext))
+        {
+            // Flexible collections is OFF, should not be using this handler
+            throw new FeatureUnavailableException("Flexible collections is OFF when it should be ON.");
+        }
+
+        if (!_currentContext.UserId.HasValue)
+        {
+            context.Fail();
+            return;
+        }
+
+        var targetOrganizationId = requirement.OrganizationId;
+
+        // Acting user is not a member of the target organization, fail
+        var org = _currentContext.GetOrganization(targetOrganizationId);
+        if (org == null)
+        {
+            context.Fail();
+            return;
+        }
+
+        switch (requirement)
+        {
+            case not null when requirement.Name == nameof(OrganizationUserOperations.Read):
+                await CanReadAsync(context, requirement, org);
+                break;
+        }
+    }
+
+    private async Task CanReadAsync(AuthorizationHandlerContext context, OrganizationUserOperationRequirement requirement,
+        CurrentContextOrganization org)
+    {
+        if (org.Type is OrganizationUserType.Owner or OrganizationUserType.Admin ||
+            org.Permissions.ManageGroups ||
+            org.Permissions.ManageUsers ||
+            org.Permissions.EditAnyCollection ||
+            org.Permissions.DeleteAnyCollection ||
+            await _currentContext.ProviderUserForOrgAsync(org.Id))
+        {
+            context.Succeed(requirement);
+            return;
+        }
+
+        context.Fail();
+    }
+}
diff --git a/src/Api/Vault/AuthorizationHandlers/OrganizationUsers/OrganizationUserOperations.cs b/src/Api/Vault/AuthorizationHandlers/OrganizationUsers/OrganizationUserOperations.cs
new file mode 100644
index 0000000000..ed0f71a50a
--- /dev/null
+++ b/src/Api/Vault/AuthorizationHandlers/OrganizationUsers/OrganizationUserOperations.cs
@@ -0,0 +1,22 @@
+using Microsoft.AspNetCore.Authorization.Infrastructure;
+
+namespace Bit.Api.Vault.AuthorizationHandlers.OrganizationUsers;
+
+public class OrganizationUserOperationRequirement : OperationAuthorizationRequirement
+{
+    public Guid OrganizationId { get; }
+
+    public OrganizationUserOperationRequirement(string name, Guid organizationId)
+    {
+        Name = name;
+        OrganizationId = organizationId;
+    }
+}
+
+public static class OrganizationUserOperations
+{
+    public static OrganizationUserOperationRequirement Read(Guid organizationId)
+    {
+        return new OrganizationUserOperationRequirement(nameof(Read), organizationId);
+    }
+}