“What a gentleman! What a phenomenal sportsman. Our Aaron Beggs,” the club said in a post in social media.
The incident was filmed by several spectators who witnessed Haridasse falling shortly after the 26 mile (41.8km) mark.
The footage showed a debilitated Haridasse making several attempts to get back on his feet while onlookers shouted encouragement.
Dozens of competitors passed the struggling athlete, until Beggs, dressed in a yellow and blue North Down Athletic Club vest, stopped to provide assistance.
He put both his hands out to pull Haridasse up off the ground, but struggled to steady the exhausted runner.
Then De Oliveira – who was on track to run his fastest-ever marathon – also paused his own race to help Beggs carry Haridasse over the line.
The pair’s selfless actions, sacrificing their own race times, prompted cheers from the crowd who were lining the finishing straight.
Spectators filmed the incident from multiple angles and posted it on social media.
At the time of writing, one of the posts has been viewed more than two million times on X.