Weatherly was involved in a collision with Ivan Romeo Mendez in 2010, which allegedly caused Mendez to be hospitalised with a neck injury and destroyed the man's BMW.
Mendez has filed a suit against Weatherly in LA, claiming that he was forced to undergo an expensive neurological procedure called rhizotomy to repair his injured neck.
In court filings, Mendez insisted that he has spent more than $80,000 (£50,687) on medical bills since the car crash.
A rep for Weatherly has not commented on the suit, according to TMZ.
Weatherly has played Special Agent Tony DiNozzo on NCIS for nine seasons and also directed an episode of the police drama earlier this year.
NCIS continues with new episode 'Thirst' on Tuesday at 8/7c on CBS.
> NCIS Michael Weatherly hints at DiNozzo romance