Mahajan formally entered politics in 2006, contesting her first election in 2009, and, despite an initial loss, rose through the ranks to become the National President of the Bharatiya Janata Yuva Morcha from December 2016 to September 2020.

She gained significant attention in the 2014 Lok Sabha elections by winning the Mumbai North Central seat, a Congress stronghold. She retained her seat in the 2019 elections by launching one of the most innovative social media campaigns in India.

In addition to her role as a legislator, Mahajan has held significant positions within the BJP, including serving as the National President of the Bharatiya Janata Yuva Morcha (BJYM) from December 2016 to September 2020.

Notably, in 2024, she was among the many sitting MPs the BJP dropped from their official candidates list.