Sen earned a Teachers' Diploma from the University of London, and continued on there as a Research Fellow, working with psychologist and professor Charles Spearman.
[4][5] Sen was persuaded to return to India by politician and poet, Sarojini Naidu, to assist in efforts to promote women's education and to participate in the Indian independence movement.
[2][1] An existing building on the grounds of Lady Irwin College is named after Hannah Sen.[3] During riots in Delhi while the Partition of India was underway, she opened the grounds of the Lady Irwin College to shelter Muslim and Sikh students from rioting Hindu mobs, despite facing threats against herself for doing so.
[6] In 1948, Sen was part of a committee constituted to advise the Government of India on the improvement of secondary education in the country.
[6] She was also invited to act as an advisor to the independent Indian government's Ministry of Relief and Rehabilitation, along with politician Rameshwari Nehru and Manmohini Zutshi Sahgal.
She was an observer at the All India Conference of Social Work in New York, 1948, and represented Indian interests at the United Nations Commissions on the Status of Women in 1950–51.