diff --git a/pkg/services/alerting/notifiers/slack.go b/pkg/services/alerting/notifiers/slack.go
index 057227e79f7..72a7b7a2c4e 100644
--- a/pkg/services/alerting/notifiers/slack.go
+++ b/pkg/services/alerting/notifiers/slack.go
@@ -382,18 +382,22 @@ func (sn *SlackNotifier) sendRequest(ctx context.Context, data []byte) error {
 		return fmt.Errorf("failed to read response body: %w", err)
 	}
 
-	if resp.StatusCode >= http.StatusOK && resp.StatusCode < http.StatusMultipleChoices {
+	if resp.StatusCode >= 200 && resp.StatusCode < 300 {
 		// Slack responds to some requests with a JSON document, that might contain an error
 		rslt := struct {
 			Ok  bool   `json:"ok"`
 			Err string `json:"error"`
 		}{}
-		if err := json.Unmarshal(body, &rslt); err == nil {
-			if !rslt.Ok && rslt.Err != "" {
-				sn.log.Warn("Sending Slack API request failed", "url", sn.url.String(), "statusCode", resp.Status,
-					"err", rslt.Err)
-				return fmt.Errorf("failed to make Slack API request: %s", rslt.Err)
-			}
+		if err := json.Unmarshal(body, &rslt); err != nil {
+			sn.log.Warn("Failed to unmarshal Slack API response", "url", sn.url.String(), "statusCode", resp.Status,
+				"err", err)
+			return fmt.Errorf("failed to unmarshal Slack API response with status code %d: %s", resp.StatusCode, err)
+		}
+
+		if !rslt.Ok && rslt.Err != "" {
+			sn.log.Warn("Sending Slack API request failed", "url", sn.url.String(), "statusCode", resp.Status,
+				"err", rslt.Err)
+			return fmt.Errorf("failed to make Slack API request: %s", rslt.Err)
 		}
 
 		sn.log.Debug("Sending Slack API request succeeded", "url", sn.url.String(), "statusCode", resp.Status)
diff --git a/pkg/services/alerting/notifiers/slack_test.go b/pkg/services/alerting/notifiers/slack_test.go
index 64be9af4e32..d0a15199bbd 100644
--- a/pkg/services/alerting/notifiers/slack_test.go
+++ b/pkg/services/alerting/notifiers/slack_test.go
@@ -273,20 +273,20 @@ func TestSendSlackRequest(t *testing.T) {
 			expectError: false,
 		},
 		{
-			name:        "Success case, no response body",
+			name:        "No response body",
 			statusCode:  http.StatusOK,
-			expectError: false,
+			expectError: true,
 		},
 		{
 			name:          "Success case, unexpected response body",
 			statusCode:    http.StatusOK,
-			slackResponse: "{}",
+			slackResponse: `{"test": true}`,
 			expectError:   false,
 		},
 		{
 			name:          "Success case, ok: true",
 			statusCode:    http.StatusOK,
-			slackResponse: "{\"ok\": true}",
+			slackResponse: `{"ok": true}`,
 			expectError:   false,
 		},
 		{
diff --git a/pkg/services/ngalert/notifier/channels/slack.go b/pkg/services/ngalert/notifier/channels/slack.go
index 85150eee979..04e9fb60247 100644
--- a/pkg/services/ngalert/notifier/channels/slack.go
+++ b/pkg/services/ngalert/notifier/channels/slack.go
@@ -218,7 +218,7 @@ var sendSlackRequest = func(request *http.Request, logger log.Logger) error {
 		return fmt.Errorf("failed to read response body: %w", err)
 	}
 
-	if resp.StatusCode < http.StatusOK || resp.StatusCode >= http.StatusMultipleChoices {
+	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
 		logger.Warn("Slack API request failed", "url", request.URL.String(), "statusCode", resp.Status, "body", string(body))
 		return fmt.Errorf("request to Slack API failed with status code %d", resp.StatusCode)
 	}
@@ -228,12 +228,16 @@ var sendSlackRequest = func(request *http.Request, logger log.Logger) error {
 		Ok  bool   `json:"ok"`
 		Err string `json:"error"`
 	}{}
-	if err := json.Unmarshal(body, &rslt); err == nil {
-		if !rslt.Ok && rslt.Err != "" {
-			logger.Warn("Sending Slack API request failed", "url", request.URL.String(), "statusCode", resp.Status,
-				"err", rslt.Err)
-			return fmt.Errorf("failed to make Slack API request: %s", rslt.Err)
-		}
+	if err := json.Unmarshal(body, &rslt); err != nil {
+		logger.Warn("Failed to unmarshal Slack API response", "url", request.URL.String(), "statusCode", resp.Status,
+			"body", string(body))
+		return fmt.Errorf("failed to unmarshal Slack API response: %s", err)
+	}
+
+	if !rslt.Ok && rslt.Err != "" {
+		logger.Warn("Sending Slack API request failed", "url", request.URL.String(), "statusCode", resp.Status,
+			"err", rslt.Err)
+		return fmt.Errorf("failed to make Slack API request: %s", rslt.Err)
 	}
 
 	logger.Debug("Sending Slack API request succeeded", "url", request.URL.String(), "statusCode", resp.Status)
diff --git a/pkg/services/ngalert/notifier/channels/slack_test.go b/pkg/services/ngalert/notifier/channels/slack_test.go
index cf2714dbbd5..2f137e40e8b 100644
--- a/pkg/services/ngalert/notifier/channels/slack_test.go
+++ b/pkg/services/ngalert/notifier/channels/slack_test.go
@@ -270,20 +270,20 @@ func TestSendSlackRequest(t *testing.T) {
 			expectError: false,
 		},
 		{
-			name:        "Success case, no response body",
+			name:        "No response body",
 			statusCode:  http.StatusOK,
-			expectError: false,
+			expectError: true,
 		},
 		{
 			name:          "Success case, unexpected response body",
 			statusCode:    http.StatusOK,
-			slackResponse: "{}",
+			slackResponse: `{"test": true}`,
 			expectError:   false,
 		},
 		{
 			name:          "Success case, ok: true",
 			statusCode:    http.StatusOK,
-			slackResponse: "{\"ok\": true}",
+			slackResponse: `{"ok": true}`,
 			expectError:   false,
 		},
 		{