diff --git a/pkg/services/ngalert/remote/alertmanager.go b/pkg/services/ngalert/remote/alertmanager.go
index 60f63cf8a32..5788506eb4c 100644
--- a/pkg/services/ngalert/remote/alertmanager.go
+++ b/pkg/services/ngalert/remote/alertmanager.go
@@ -285,7 +285,7 @@ func (am *Alertmanager) isDefaultConfiguration(configHash [16]byte) bool {
 	return fmt.Sprintf("%x", configHash) == am.defaultConfigHash
 }
 
-// decryptConfiguration decrypts the configuration in-place and returns the decrypted configuration alongside its hash.
+// decryptConfiguration creates a copy of the configuration, decrypts it, and returns the decrypted configuration alongside its hash.
 // Should not be used outside of this package and the specific use case of decrypting the configuration before sending
 // it to the remote Alertmanager.
 func (am *Alertmanager) decryptConfiguration(ctx context.Context, cfg *apimodels.PostableUserConfig) ([]byte, [16]byte, error) {
@@ -293,10 +293,18 @@ func (am *Alertmanager) decryptConfiguration(ctx context.Context, cfg *apimodels
 		return am.decrypt(ctx, payload)
 	}
 
-	// Iterate through receivers and decrypt secure settings.
-	// It's not necessary to be careful about not modifying the original, as it's used only in a specific context where
-	// the config is read from json and then immediately sent to the remote Alertmanager.
-	for _, rcv := range cfg.AlertmanagerConfig.Receivers {
+	// Create a copy of the configuration to avoid modifying the original
+	cfgCopy := &apimodels.PostableUserConfig{}
+	rawCfg, err := json.Marshal(cfg)
+	if err != nil {
+		return nil, [16]byte{}, fmt.Errorf("unable to marshal original configuration: %w", err)
+	}
+	if err := json.Unmarshal(rawCfg, cfgCopy); err != nil {
+		return nil, [16]byte{}, fmt.Errorf("unable to unmarshal original configuration: %w", err)
+	}
+
+	// Iterate through receivers and decrypt secure settings on the copy
+	for _, rcv := range cfgCopy.AlertmanagerConfig.Receivers {
 		for _, gmr := range rcv.GrafanaManagedReceivers {
 			decrypted, err := gmr.DecryptSecureSettings(fn)
 			if err != nil {
@@ -306,7 +314,7 @@ func (am *Alertmanager) decryptConfiguration(ctx context.Context, cfg *apimodels
 		}
 	}
 
-	rawDecrypted, err := json.Marshal(cfg)
+	rawDecrypted, err := json.Marshal(cfgCopy)
 	if err != nil {
 		return nil, [16]byte{}, fmt.Errorf("unable to marshal decrypted configuration: %w", err)
 	}
diff --git a/pkg/services/ngalert/remote/alertmanager_test.go b/pkg/services/ngalert/remote/alertmanager_test.go
index 0fcd1e8f93e..85f88c1c613 100644
--- a/pkg/services/ngalert/remote/alertmanager_test.go
+++ b/pkg/services/ngalert/remote/alertmanager_test.go
@@ -43,7 +43,18 @@ import (
 	"github.com/grafana/grafana/pkg/util"
 )
 
+var (
+	testPasswordBase64   = base64.StdEncoding.EncodeToString([]byte(testPassword))
+	defaultGrafanaConfig = setting.GetAlertmanagerDefaultConfiguration()
+	errTest              = errors.New("test")
+
+	// Valid Grafana Alertmanager configuration with secret in base64.
+	testGrafanaConfigWithEncryptedSecret = fmt.Sprintf(`{"template_files":{},"alertmanager_config":{"time_intervals":[{"name":"weekends","time_intervals":[{"weekdays":["saturday","sunday"],"location":"Africa/Accra"}]}],"route":{"receiver":"grafana-default-email","group_by":["grafana_folder","alertname"]},"receivers":[{"name":"grafana-default-email","grafana_managed_receiver_configs":[{"uid":"dde6ntuob69dtf","name":"WH","type":"webhook","disableResolveMessage":false,"settings":{"url":"http://localhost:8080","username":"test"},"secureSettings":{"password":"%s"}}]}]}}`, testPasswordBase64)
+)
+
 const (
+	testPassword = "test"
+
 	// Valid Grafana Alertmanager configurations.
 	testGrafanaConfig                               = `{"template_files":{},"alertmanager_config":{"time_intervals":[{"name":"weekends","time_intervals":[{"weekdays":["saturday","sunday"],"location":"Africa/Accra"}]}],"route":{"receiver":"grafana-default-email","group_by":["grafana_folder","alertname"]},"receivers":[{"name":"grafana-default-email","grafana_managed_receiver_configs":[{"uid":"","name":"some other name","type":"email","disableResolveMessage":false,"settings":{"addresses":"\u003cexample@email.com\u003e"}}]}]}}`
 	testGrafanaConfigWithSecret                     = `{"template_files":{},"alertmanager_config":{"time_intervals":[{"name":"weekends","time_intervals":[{"weekdays":["saturday","sunday"],"location":"Africa/Accra"}]}],"route":{"receiver":"grafana-default-email","group_by":["grafana_folder","alertname"]},"receivers":[{"name":"grafana-default-email","grafana_managed_receiver_configs":[{"uid":"dde6ntuob69dtf","name":"WH","type":"webhook","disableResolveMessage":false,"settings":{"url":"http://localhost:8080","username":"test"},"secureSettings":{"password":"test"}}]}]}}`
@@ -56,11 +67,6 @@ const (
 	testNflog2   = "OgoqCgZncm91cDISEgoJcmVjZWl2ZXIyEgV0ZXN0MyoMCLSDkbAGEMvaofYCEgwIxJ+RsAYQy9qh9gI6CioKBmdyb3VwMRISCglyZWNlaXZlcjESBXRlc3QzKgwItIORsAYQy9qh9gISDAjEn5GwBhDL2qH2Ag=="
 )
 
-var (
-	defaultGrafanaConfig = setting.GetAlertmanagerDefaultConfiguration()
-	errTest              = errors.New("test")
-)
-
 func TestMain(m *testing.M) {
 	testsuite.Run(m)
 }
@@ -505,6 +511,44 @@ func Test_isDefaultConfiguration(t *testing.T) {
 	}
 }
 
+func TestDecryptConfiguration(t *testing.T) {
+	t.Run("should not modify the original config", func(t *testing.T) {
+		var inputCfg apimodels.PostableUserConfig
+		require.NoError(t, json.Unmarshal([]byte(testGrafanaConfigWithEncryptedSecret), &inputCfg))
+
+		decryptFn := func(_ context.Context, payload []byte) ([]byte, error) {
+			if string(payload) == testPassword {
+				return []byte(testPassword), nil
+			}
+			return nil, fmt.Errorf("incorrect payload")
+		}
+
+		am := &Alertmanager{
+			decrypt: decryptFn,
+		}
+
+		rawDecrypted, _, err := am.decryptConfiguration(context.Background(), &inputCfg)
+		require.NoError(t, err)
+
+		currentJSON, err := json.Marshal(inputCfg)
+		require.NoError(t, err)
+		require.JSONEq(t, testGrafanaConfigWithEncryptedSecret, string(currentJSON), "Original configuration should not be modified")
+
+		var decryptedCfg apimodels.PostableUserConfig
+		require.NoError(t, json.Unmarshal(rawDecrypted, &decryptedCfg))
+
+		found := false
+		for _, rcv := range decryptedCfg.AlertmanagerConfig.Receivers {
+			for _, gmr := range rcv.GrafanaManagedReceivers {
+				if gmr.Type == "webhook" && gmr.SecureSettings["password"] == testPassword {
+					found = true
+				}
+			}
+		}
+		require.True(t, found, "Decrypted configuration should contain decrypted password")
+	})
+}
+
 func TestIntegrationRemoteAlertmanagerConfiguration(t *testing.T) {
 	if testing.Short() {
 		t.Skip("skipping integration test")