Police were called just after midnight to reports of a gunshot being heard in Crabtree, Paston.
Emergency services including paramedics and police officers attended the scene following which the man was taken to hospital.
A police spokesperson said: “We were called at 12.34am today (April 13) with reports of a gunshot being heard in Crabtree, Peterborough.
Investigation has been launched and a police cordon is currently in place in Crabtree and scientific units are also present on the scene of the incident.
A grey Toyota Auris – with smashed back window is also part of the police cordon.
A spokesman for Cambridgeshire police said: “Officers and paramedics attended the scene.
“A 29-year-old man was taken to hospital for treatment, where he remains in a critical condition.
“An investigation is ongoing, and a scene remains in place. No arrests have yet been made.
"Although we believe the wider public is not at any risk following this incident, we are increasing patrols in the area.
“Anyone with information about what happened is urged to contact police via their web chat service or online forms quoting incident 13 of 13 April. "
Anyone without internet access should call 101. Always dial 999 in an emergency.