A man is in critical condition with serious head injuries after he jumped out of a moving taxi on Sunday morning in Melbourne's east.

The man, aged in his 20s, was travelling in a maxi taxi along Mount Dandenong Road in Croydon about 5.20am when he opened the van's door and jumped out.

Ambulance Victoria spokesman Paul Bentley said the Heathmont man was stabilised at the scene by paramedics before being taken to the Royal Melbourne Hospital.

The man remains in a critical condition, a hospital spokeswoman said.

No charges have been laid over the incident.