Police arrested 43-year-old Richard Downes on Saturday.
A woman who was riding the 8a Suffolk County transit bus claims Downes pulled over, forced her to the back of the bus and tried to sexually assault her.
She says when she fought back, Downes stopped.
The woman was the only passenger aboard the bus when the incident happened near the Suffolk County Center in Riverside.
Downes is charged with attempted rape and unlawful imprisonment.