Three to Tango

A rich businessman's assumption that his new colleague is gay leads him to ask the man to keep an eye on his mistress. However, the man is not gay--and he begins to fall for the woman himself.

Three to Tango is a 1999 romance comedy movie directed by Damon Santostefano, starring Neve Campbell, Dylan McDermott, Matthew Perry. It holds an IMDb rating of 6.1/10 from 20,901 votes and runs 1h 38m.