Starting his career in the late 1960s, Mahajan worked simultaneously in parallel and mainstream films for the next four decades. In all he shot 84 feature films, around 100 commercials and over 20 documentaries and several television serials.[3]
Mahajan started his career worked on advertising films, short films and documentaries most notably Shyam Benegal's Child of the Streets (1967), Kumar Shahani's A Certain Childhood (1967), and BD Garga's Amrita Shergil (1968) and Mahabalipuram (1968).[4]
After Char Adhyay (1997) directed Kumar Shahani he did few films, Ekti Nadir Naam directed by Anup Singh was the last film shot by him in 2002. He was diagnosed with throat cancer and as a result his voice-box was removed. Thereafter he shot no other feature film, though he shot a small documentary in 2005, directed by Kumar Shahani about the mounting of an exhibition of painter Akbar Padamsee.[2]
In 2003, the Indian Society of Cinematographers (ISC) awarded him an Honorary Membership, along with A. Vincent and V. K. Murthy.[6] In 2002, he received the Ezra Mir Award for Lifetime Achievement at the IDPA Awards 2005 of Indian Documentary Producers Association (IDPA).[3][7]
His cancer returned in his last months and eventually he died in Mumbai on 13 July 2007.[4] His last release was Yaar Meri Zindagi starring Amitabh Bachchan and Shatrughan Sinha. The film was shot in 1971, but released only in 2008, due to legal issues.[8]