diff --git a/pkg/services/ngalert/api/api_ruler.go b/pkg/services/ngalert/api/api_ruler.go
index e79a280ca94..1b34667456e 100644
--- a/pkg/services/ngalert/api/api_ruler.go
+++ b/pkg/services/ngalert/api/api_ruler.go
@@ -230,6 +230,7 @@ func (srv RulerSrv) RoutePostNameRulesConfig(c *models.ReqContext, ruleGroupConf
 		return response.Error(http.StatusBadRequest, "rule group name is not valid", nil)
 	}
 
+	var alertRuleUIDs []string
 	for _, r := range ruleGroupConfig.Rules {
 		cond := ngmodels.Condition{
 			Condition: r.GrafanaManagedAlert.Condition,
@@ -239,6 +240,7 @@ func (srv RulerSrv) RoutePostNameRulesConfig(c *models.ReqContext, ruleGroupConf
 		if err := validateCondition(cond, c.SignedInUser, c.SkipCache, srv.DatasourceCache); err != nil {
 			return response.Error(http.StatusBadRequest, fmt.Sprintf("failed to validate alert rule %s", r.GrafanaManagedAlert.Title), err)
 		}
+		alertRuleUIDs = append(alertRuleUIDs, r.GrafanaManagedAlert.UID)
 	}
 
 	if err := srv.store.UpdateRuleGroup(store.UpdateRuleGroupCmd{
@@ -254,6 +256,10 @@ func (srv RulerSrv) RoutePostNameRulesConfig(c *models.ReqContext, ruleGroupConf
 		return response.Error(http.StatusInternalServerError, "failed to update rule group", err)
 	}
 
+	for _, uid := range alertRuleUIDs {
+		srv.manager.RemoveByRuleUID(c.OrgId, uid)
+	}
+
 	return response.JSON(http.StatusAccepted, util.DynMap{"message": "rule group updated successfully"})
 }
 
diff --git a/pkg/services/ngalert/store/alert_rule.go b/pkg/services/ngalert/store/alert_rule.go
index 23fa5e68bb2..5b1e7cf2707 100644
--- a/pkg/services/ngalert/store/alert_rule.go
+++ b/pkg/services/ngalert/store/alert_rule.go
@@ -40,6 +40,7 @@ type RuleStore interface {
 	DeleteAlertRuleByUID(orgID int64, ruleUID string) error
 	DeleteNamespaceAlertRules(orgID int64, namespaceUID string) ([]string, error)
 	DeleteRuleGroupAlertRules(orgID int64, namespaceUID string, ruleGroup string) ([]string, error)
+	DeleteAlertInstancesByRuleUID(orgID int64, ruleUID string) error
 	GetAlertRuleByUID(*ngmodels.GetAlertRuleByUIDQuery) error
 	GetAlertRulesForScheduling(query *ngmodels.ListAlertRulesQuery) error
 	GetOrgAlertRules(query *ngmodels.ListAlertRulesQuery) error
@@ -157,6 +158,17 @@ func (st DBstore) DeleteRuleGroupAlertRules(orgID int64, namespaceUID string, ru
 	return ruleUIDs, err
 }
 
+// DeleteAlertInstanceByRuleUID is a handler for deleting alert instances by alert rule UID when a rule has been updated
+func (st DBstore) DeleteAlertInstancesByRuleUID(orgID int64, ruleUID string) error {
+	return st.SQLStore.WithTransactionalDbSession(context.Background(), func(sess *sqlstore.DBSession) error {
+		_, err := sess.Exec("DELETE FROM alert_instance WHERE def_org_id = ? AND def_uid = ?", orgID, ruleUID)
+		if err != nil {
+			return err
+		}
+		return nil
+	})
+}
+
 // GetAlertRuleByUID is a handler for retrieving an alert rule from that database by its UID and organisation ID.
 // It returns ngmodels.ErrAlertRuleNotFound if no alert rule is found for the provided ID.
 func (st DBstore) GetAlertRuleByUID(query *ngmodels.GetAlertRuleByUIDQuery) error {
@@ -507,6 +519,15 @@ func (st DBstore) UpdateRuleGroup(cmd UpdateRuleGroupCmd) error {
 			return err
 		}
 
+		// delete instances for rules that will not be removed
+		for _, rule := range existingGroupRules {
+			if _, ok := existingGroupRulesUIDs[rule.UID]; !ok {
+				if err := st.DeleteAlertInstancesByRuleUID(cmd.OrgID, rule.UID); err != nil {
+					return err
+				}
+			}
+		}
+
 		// delete the remaining rules
 		for ruleUID := range existingGroupRulesUIDs {
 			if err := st.DeleteAlertRuleByUID(cmd.OrgID, ruleUID); err != nil {