Michael McIntyre was targeted by thieves on a moped on Monday during his school run.
The comedian was in his parked Range Rover when two males smashed the car windows with a hammer and stole his £5,000 watch.
The attack happened at 2pm in Hampstead, north-west London, while McIntyre was with one of his children.
Michael McIntyre is one of thousands of people - including a handful of household names - affected by a surge in moped-related crime in London.
The 42-year-old comedian was reportedly forced to hand over his watch after being confronted by gang of hammer-wielding thieves on two wheels.
Others to have fallen victim to so-called moped gangs include MoneySavingExpert.com founder Martin Lewis, whose phone was snatched from his hands last July, while actor Daniel Radcliffe came to the aid of a tourist who was mugged.
Figures from 2017 suggested that, between January and September, there were more than 19,385 "moped enabled" crimes in the capital - an average of 53 a day - including thefts and robberies.
At the time, police said they were tackling the increase three ways: a UV spray, mobile stinger and more lightweight motorbikes for officers.
Officers said there are a number of factors behind the upward spike in thefts, including a rise in the number of people using scooters to commute and a growing market for second-hand mobile phone parts.
Scooter criminals normally travel in pairs, with a passenger sitting behind the rider, targeting busy areas where they can snatch high-value smartphones.
Youths even carry out dry runs to practise before launching the real raids, detectives believe, while it is thought in some cases mobiles are stolen to order.
Speaking last October, Metropolitan Police Commissioner Cressida Dick said: "I think we are stemming the rise but I want sustained reductions."