The female Garda officer was first on the scene and performed CPR. Off-duty Dublin Fire Brigade (DFB) officer Ben Weddick who was competing in the race stopped and assisted in the CPR when he came to the scene.
The man was later rushed to hospital and is said to be making a good recovery.
Never off-duty: FF/P Ben Weddick and @GardaTraffic member achieved a ROSC after witnessing a cardiac arrest at today's Dublin Half Marathon. pic.twitter.com/Uu0q6aZ5wz— Dublin Fire Brigade (@DubFireBrigade) September 24, 2016