Sekhar is Emeritus Professor of History. He was the founding Director of the New Zealand India Research Institute.

Educated at Presidency College and University of Calcutta, his primary research interest is in the history of nationalism and caste in colonial and postcolonial India. He is also interested in the history of Indian migration and the Indian diaspora. He has written six books, edited or co-edited fourteen books, and published more than fifty book chapters and journal articles. His most recent co-authored book is Caste and Partition in Bengal: The Story of Dalit Refugees, 1946-1961 (OUP, 2022). Some of his other books are From Plassey to Partition and After: A History of Modern India (Second edition, Orient BlackSwan, 2015), Caste, Protest and Identity in Colonial India: The Namasudras of Bengal, 1872-1947 (Second edition, OUP, 2011), Decolonization in South Asia: Meanings of Freedom in Post-independence West Bengal (Routledge, 2009/Orient BlackSwan 2012), Caste, Culture and Hegemony: Social Dominance in Colonial Bengal (Sage, 2004). He has recently co-edited The Long History of Partition in Bengal: Event, Memory, Representations (Routledge, 2024), Caste in Bengal: Histories of Hierarchy, Exclusion and Resistance (Permanent Black, in association with Ashoka University, 2022), Indians and the Antipodes: Networks, Boundaries and Circulation (OUP, 2018), Religion and Modernity in India (OUP, 2016), Calcutta: The Stormy Decades (Routledge, 2018/Social Science Press, 2015).

He has been visiting fellow at University of Chicago, Australian National University, National University of Singapore, School of Oriental and African Studies, International Institute of Asian Studies (Leiden), Curtin University, Calcutta University and Rabindra Bharati University. He is co-editor of the New Zealand Journal of Asian Studies. He is an Inaugural Fellow of the New Zealand Academy of Humanities and a Fellow of the Royal Society of New Zealand. He is a recipient of Rabindra Puraskar (Rabindranath Tagore Award), given by Bangla Academy, Government of West Bengal, India.