Leonard and Priya first met on April 12, 2005. Howard and Leonard pinky swore 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. 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.
In the episode "The Good Guy Fluctuation", Leonard is distraught after he kissed Alice, and feels that he have 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 a few weeks back. Priya tells Leonard that their 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, as in the next episode, he refers to himself as single.
Priya is also verbally abused by Penny, Bernadette and Amy who are annoyed at her because of her controlling nature in which she forces Leonard not to talk to Penny and cut ties with her though they never do this in front of her. Penny is also secretly heartbroken and drinking a lot over Leonard's relationship with Priya although she also hides this from Leonard.