A cyclist has had a lucky escape after being involved in a crash with two semi-trailers on Sydney's north shore.

Emergency services raced to Mona Vale Road in St Ives just after 6am on Wednesday after two trucks collided and a cyclist, who was riding behind, smashed into one of them.

The cyclist, a man in his 20s, has been taken to Royal North Shore Hospital with non life-threatening injuries, police said.