Three to Tango (1999) on Netflix

Oscar Novak is an idealistic, young architect on the rise. Boyishly handsome and funny, Oscar and his business partner, Peter Steinberg, have just landed a career-making opportunity-Chicago tycoon Charles Newman has chosen them to compete for the design of a multi-million dollar cultural center. In a ploy for publicity, Newman has pitched Oscar and Peter in a neck-and-neck competition with their arch rivals and former colleagues, the hugely successful (and equally ruthless) Decker and Strauss. Impressed with Oscar's feverish dedication to winning the job, Charles assigns him the additional task of spying on his mistress, Amy, a woman who Charles guards as jealously as he guards his investments. Oscar's bumbling attempts at surveillance fail, but he does develop a crush on Amy, a beautiful and headstrong artist, who begins to return his growing affection. Much to his chagrin, Oscar may have finally found the woman of his dreams. But Oscar's dream is short-lived when he discovers that the jealous Charles has assigned him this special job only because he (mistakenly) believes that Oscar is gay. Oscar's frustration compounds when he realizes that Amy also believes him to be gay. In short order, Oscar's friends, his family, even strangers on the street believe that he is gay. The very heterosexual Oscar Novak becomes the most famous gay man in Chicago, and his entire life is turned upside-down. When he is honored as Chicago's Gay Professional of the Year, Oscar has to make a decision-will he continue the lie and hold on to the job of a lifetime and a warm but frustrating friendship with the girl he loves, or is it time to face the consequences of coming out of the closet and telling the whole world that he is secretly... straight?