Hari Sen was born in 1955 in the royal family of Suket, an erstwhile 11-gun salute princely state whose capital used to be the present-day town of Sundar Nagar in Himachal Pradesh.

Sen's mother was Krishna Kumari, daughter of Maharawal Sir Lakshman Singh (the last ruling king of Dungarpur) from his second wife.

[3] His PhD dissertation was titled Popular Protest in Mewar in the Late-Nineteenth and Early-Twentieth Centuries (unpublished, 1996).

[14][15] Sen taught history at Ramjas College, Delhi University, from October 1991 till his retirement in August 2020.

[6][19][20] He has been mentioned as an influence in the works of several historians and other scholars of South Asia, including Ramchandra Guha (2000),[21] Prakash Kumar (2012),[22] Monika Saxena (2018),[23] Pankaj Jha (2018),[24] Radhika Chopra (2018),[25] and Nikhil Menon (2022).