Murali (Naran aka Sunil) with his golden voice is the doyen of the college campus. P. Sukumaran (Prithviraj) is a firebrand student leader with leanings towards the left. Satheesan (Jayasurya) leads the opposite faction. Vasu (Vijeesh) is his trusted crony. Pius (Indrajith), a rich and spoiled brat and son of Gulf settled parents, is the campus Romeo. Thara Kurup (Kavya Madhavan) is the daughter of the local MLA and a danseuse who wins numerous awards for the college with her performance. Koshy (Jagathy Sreekumar) is the hostel warden.

It was Murali's dream that these classmates should have a reunion ten years from graduation. But Murali dies under mysterious circumstances. His parents Prof. Iyengar (Balachandra Menon) and Lakshmi Teacher (Shobha Mohan) who both teach at the college decide to fulfill their departed son's dream and bring his classmates together for a reunion. Sukumaran is now a diamond dealer in Mumbai. Satheesan is now an MLA. Vasu continues to be his sidekick. Pius is now settled in the Gulf. Thara, still unmarried, now runs a dancing school.

The coming together of these classmates is an occasion for the participants to regurgitate the past and go nostalgic. Though Classmates is a campus based movie, this is not going to be sugar candy romance. Lal Jose's intention is to throw in emotion and suspense as well as the colour and gaiety of campus life and to make a movie in the manner of Ulkkadal, Shalini Ente Koottukaari and Sarvakalaasaala. The campus scenes are shot at CMS College, Kottayam.