Leonard and Priya first met on April 12, 2005. Howard and Leonard made a pinky swear not to hit on her, but it was revealed that Leonard had sexual relations with her, which the other guys did not know about.
They meet each other again in "The Irish Pub Formulation", and officially start dating in "The Cohabitation Formulation", but it doesn't last because she moves back to India. On more than one occasion, Priya has avoided telling her parents or have her parents know she is dating Leonard. Her parents prefer her dating an Indian gentleman. This is a big issue with Leonard and has caused a lot of arguments between the two. Priya has a slightly superior attitude toward others and can be controlling. She objects to Leonard hanging out with his ex-girlfriend Penny, who realizes this situation and tells Leonard "good-bye". Later, when the gang is at the hospital waiting for word on Howard's mother, Penny and Priya start to bond together over Leonard's foibles.
In the episode "The Good Guy Fluctuation", Leonard is distraught after he kissed Alice, and feels that he has to tell Priya that it is a one-time-thing, which does not mean anything. He confesses to her and she replies that it is fine. Her words confuse Leonard and she tells him that she had sex with her ex-boyfriend. So both strayed. Priya tells Leonard that their cheating actions are not a contest to which Leonard disagreed telling Priya that it is and she won. He then excuses himself and closes his laptop exclaiming that he does not believe it. It is assumed that Leonard breaks up with her later or they never talked again, as in the next episode, he refers to himself as single.