Sirf Tum revolves around Deepak, an ordinary young man with a big heart, and Aarthi, an attractive, middle class girl. While in Dehli, Deepak finds a lost handbag belonging to Aarthi. Returning it to her, Deepak begins writing her on a regular basis.
Eventually, the two fall in love. While exchanging letters, the two meet each other at random times but both have no idea who the other is. The necessary plot twist comes in the way of Neha, Deepak's boss, who falls in love with him and tries to woo him. The rest of the movie concentrates on whether Deepak rejects the advances of Neha and meets Aarthi.