A young construction worker has suffered serious head injuries after falling about five metres from scaffolding at a worksite in Melbourne's north.

The man, aged in his early 20s, was working at a Fitzroy North site about 7.30am on Tuesday when he fell several metres below ground level and hit his head.

The worker was winched to safety on a stretcher by the Metropolitan Fire Brigade and paramedics believe he may have also suffered spinal injuries.

He was taken to the Royal Melbourne Hospital in a stable condition.

WorkSafe is investigating the fall.