Crusaders kept up their pursuit of league leaders Linfield and dented Cliftonville's hopes of retaining their title by winning the derby at Solitude.
Paul Heatley scored the 60th-minute winner when he swept the ball into the bottom left-hand corner after Gavin Whyte squared the ball from the right.
The Reds had chances to equalise but Sean O'Neill denied a David McDaid volley a late Jude Winchester effort.
Barry Johnston came off in the first half after suffering a broken kneecap.
The result sees Crusaders move into a clear second position in the Premiership, four points behind the pacesetting Blues, while Cliftonville drop to fourth, seven behind Linfield.
McDaid had the best chance of an uneventful first half, but O'Neill was equal to the task with a fine stop, while Winchester came on for Johnston, who was carried off.
After the interval, Chris Curran curled a right-foot shot wide of the post and Heatley volleyed over the top at the other end.
Heatley's 12th goal of the season proved the decisive moment of this north Belfast derby as Tommy Breslin's side were unable to find a response.
Jordan Owens had an opportunity soon after Heatley's strike but Conor Devlin produced a fine save from the striker.
Crusaders manager Stephen Baxter: "This was a big game for both teams and we're pleased to get the three points. It was very tight throughout and there wasn't much between the sides.
"Gavin Whyte had a super game and produced a fine cross for Paul Heatley, who had a quieter game, but came up with the winner - he gets into dangerous positions and he's always a threat.
"Linfield are still in the box seat - we have it all to do as we are chasing them. It's all about staying in the race at this time of year, as we haven't been able to stay in touch in recent seasons. Now we face another big test against Linfield."