A male HSBC vice president and senior product manager in New York says he was falsely accused of sexually harassing a female colleague and then fired because he is a man.

The March 27 sex discrimination lawsuit not only is one of the rare instances of sex bias allegations being brought by a man, it also comes with an added twist: Hussam Hariri says it was his female colleague who did the harassing.

The bank’s human resources department presumed Hariri was guilty of harassing her before even launching an investigation into her complaint, he claims.

HSBC has “no comment as...