The 2011 world champion suffered a bruised arm in the incident which is reported to have occurred near his Italian home in Quarrata, Tuscany.
Cavendish, who is joining Omega Pharma-Quick Step in 2013 after one season with Team Sky, tweeted: "Went & hit the back of a car that slammed on today in training. Wasn't ideal. Apart from a bruised arm, I'm relatively ok. If anyone cares."
The incident occurs in the same month that Bradley Wiggins and British Cycling's head coach Shane Sutton were involved in serious crashes.
Sutton was taken to hospital after suffering bruising and bleeding on the brain in an accident 10 days ago, a day after British Olympic time trial champion Wiggins suffered a fractured rib, a bruised lung and a dislocated finger following a collision with a van in Lancashire.
It is also reported that Cavendish has got engaged to girlfriend Peta Todd.