diff --git a/lib/auth/join_azure.go b/lib/auth/join_azure.go
index 81d8aea501354..e044d4e810a69 100644
--- a/lib/auth/join_azure.go
+++ b/lib/auth/join_azure.go
@@ -25,6 +25,7 @@ import (
 	"encoding/pem"
 	"net/url"
 	"slices"
+	"strings"
 	"time"
 
 	"github.com/Azure/azure-sdk-for-go/sdk/azcore"
@@ -286,15 +287,31 @@ func checkAzureAllowRules(vm *azure.VirtualMachine, token string, allowRules []*
 		if rule.Subscription != vm.Subscription {
 			continue
 		}
-		if len(rule.ResourceGroups) > 0 {
-			if !slices.Contains(rule.ResourceGroups, vm.ResourceGroup) {
-				continue
-			}
+		if !azureResourceGroupIsAllowed(rule.ResourceGroups, vm.ResourceGroup) {
+			continue
 		}
 		return nil
 	}
 	return trace.AccessDenied("instance %v did not match any allow rules in token %v", vm.Name, token)
 }
+func azureResourceGroupIsAllowed(allowedResourceGroups []string, vmResourceGroup string) bool {
+	if len(allowedResourceGroups) == 0 {
+		return true
+	}
+
+	// ResourceGroups are case insensitive.
+	// https://learn.microsoft.com/en-us/azure/azure-resource-manager/management/frequently-asked-questions#are-resource-group-names-case-sensitive
+	// The API returns them using capital case, but docs don't mention a specific case.
+	// Converting everything to the same case will ensure a proper comparison.
+	resourceGroup := strings.ToUpper(vmResourceGroup)
+	for _, allowedResourceGroup := range allowedResourceGroups {
+		if strings.EqualFold(resourceGroup, allowedResourceGroup) {
+			return true
+		}
+	}
+
+	return false
+}
 
 func (a *Server) checkAzureRequest(ctx context.Context, challenge string, req *proto.RegisterUsingAzureMethodRequest, cfg *azureRegisterConfig) error {
 	requestStart := a.clock.Now()
diff --git a/lib/auth/join_azure_test.go b/lib/auth/join_azure_test.go
index 3c3e7d9078b8e..5fe5d487fcf3a 100644
--- a/lib/auth/join_azure_test.go
+++ b/lib/auth/join_azure_test.go
@@ -190,7 +190,7 @@ func TestAuth_RegisterUsingAzureMethod(t *testing.T) {
 			tokenName:        "test-token",
 			requestTokenName: "test-token",
 			subscription:     subID,
-			resourceGroup:    "rg",
+			resourceGroup:    "RG",
 			tokenSpec: types.ProvisionTokenSpecV2{
 				Roles: []types.SystemRole{types.RoleNode},
 				Azure: &types.ProvisionTokenSpecV2Azure{
@@ -207,12 +207,34 @@ func TestAuth_RegisterUsingAzureMethod(t *testing.T) {
 			certs:       []*x509.Certificate{tlsConfig.Certificate},
 			assertError: require.NoError,
 		},
+		{
+			name:             "resource group is case insensitive",
+			tokenName:        "test-token",
+			requestTokenName: "test-token",
+			subscription:     subID,
+			resourceGroup:    "my-RESOURCE-GROUP",
+			tokenSpec: types.ProvisionTokenSpecV2{
+				Roles: []types.SystemRole{types.RoleNode},
+				Azure: &types.ProvisionTokenSpecV2Azure{
+					Allow: []*types.ProvisionTokenSpecV2Azure_Rule{
+						{
+							Subscription:   subID,
+							ResourceGroups: []string{"MY-resource-group"},
+						},
+					},
+				},
+				JoinMethod: types.JoinMethodAzure,
+			},
+			verify:      mockVerifyToken(nil),
+			certs:       []*x509.Certificate{tlsConfig.Certificate},
+			assertError: require.NoError,
+		},
 		{
 			name:             "wrong token",
 			tokenName:        "test-token",
 			requestTokenName: "wrong-token",
 			subscription:     subID,
-			resourceGroup:    "rg",
+			resourceGroup:    "RG",
 			tokenSpec: types.ProvisionTokenSpecV2{
 				Roles: []types.SystemRole{types.RoleNode},
 				Azure: &types.ProvisionTokenSpecV2Azure{
@@ -233,7 +255,7 @@ func TestAuth_RegisterUsingAzureMethod(t *testing.T) {
 			tokenName:        "test-token",
 			requestTokenName: "test-token",
 			subscription:     subID,
-			resourceGroup:    "rg",
+			resourceGroup:    "RG",
 			tokenSpec: types.ProvisionTokenSpecV2{
 				Roles: []types.SystemRole{types.RoleNode},
 				Azure: &types.ProvisionTokenSpecV2Azure{
@@ -255,7 +277,7 @@ func TestAuth_RegisterUsingAzureMethod(t *testing.T) {
 			tokenName:        "test-token",
 			requestTokenName: "test-token",
 			subscription:     "some-junk",
-			resourceGroup:    "rg",
+			resourceGroup:    "RG",
 			tokenSpec: types.ProvisionTokenSpecV2{
 				Roles: []types.SystemRole{types.RoleNode},
 				Azure: &types.ProvisionTokenSpecV2Azure{
@@ -276,7 +298,7 @@ func TestAuth_RegisterUsingAzureMethod(t *testing.T) {
 			tokenName:        "test-token",
 			requestTokenName: "test-token",
 			subscription:     subID,
-			resourceGroup:    "wrong-rg",
+			resourceGroup:    "WRONG-RG",
 			tokenSpec: types.ProvisionTokenSpecV2{
 				Roles: []types.SystemRole{types.RoleNode},
 				Azure: &types.ProvisionTokenSpecV2Azure{
@@ -298,7 +320,7 @@ func TestAuth_RegisterUsingAzureMethod(t *testing.T) {
 			tokenName:        "test-token",
 			requestTokenName: "test-token",
 			subscription:     subID,
-			resourceGroup:    "rg",
+			resourceGroup:    "RG",
 			tokenSpec: types.ProvisionTokenSpecV2{
 				Roles: []types.SystemRole{types.RoleNode},
 				Azure: &types.ProvisionTokenSpecV2Azure{
@@ -322,7 +344,7 @@ func TestAuth_RegisterUsingAzureMethod(t *testing.T) {
 			tokenName:        "test-token",
 			requestTokenName: "test-token",
 			subscription:     subID,
-			resourceGroup:    "rg",
+			resourceGroup:    "RG",
 			tokenSpec: types.ProvisionTokenSpecV2{
 				Roles: []types.SystemRole{types.RoleNode},
 				Azure: &types.ProvisionTokenSpecV2Azure{
@@ -343,7 +365,7 @@ func TestAuth_RegisterUsingAzureMethod(t *testing.T) {
 			tokenName:        "test-token",
 			requestTokenName: "test-token",
 			subscription:     subID,
-			resourceGroup:    "rg",
+			resourceGroup:    "RG",
 			vmID:             "vm-id",
 			tokenSpec: types.ProvisionTokenSpecV2{
 				Roles: []types.SystemRole{types.RoleNode},
@@ -358,7 +380,7 @@ func TestAuth_RegisterUsingAzureMethod(t *testing.T) {
 			},
 			vmResult: &azure.VirtualMachine{
 				Subscription:  subID,
-				ResourceGroup: "rg",
+				ResourceGroup: "RG",
 				VMID:          "different-id",
 			},
 			verify:      mockVerifyToken(nil),