As a college student, Mahajan was an active member of ABVP in 1978.[3] In the ABVP, he started as a grassroots worker where he painted walls and distributed promotional posters for politicians. He was appointed Taluka President of ABVP.

Mahajan’s political career commenced in earnest in the early eighties, when he became Taluka President of the Bharatiya Janata Yuva Morcha (youth wing of the BJP) in Maharashtra.

In 1992, Mahajan was elected as a Gram-Panchayat election for Jamner.