Before moving to the Central University of Kerala as Professor in March 2023, Dr Rajendran has been working as Principal Scientist & Head, Division of Aquatic Environment & Health Management,  and Dean (Academics), Central Institute of Fisheries Education, Mumbai, a Deemed University under the Indian Council of Agricultural Research (ICAR).  

He entered the Agricultural Research Service (ARS) in 1992 and joined ICAR-Central Institute of Brackishwater Aquaculture, Chennai, as Scientist in 1993; moved to ICAR-Central Institute of Fisheries Education as Senior Scientist and, became Principal Scientist in 2006. 

As a recipient of the Korea Science and Engineering Foundation (KOSEF) post-doctoral fellowship, he worked at Yeosu National University, South Korea (2000-2001) on hybridoma technology; worked as Fish Pathologist at the Commonwealth Scientific & Industrial Research Organization (CSIRO), Australia (2003-2006) and under the Fulbright-Nehru Senior Research Fellowship worked at the Auburn University, USA (2011) on molecular immunology of fish. Dr. Rajendran has led various institutional and extramural research projects including an international collaborative project on different aspects of fish and shellfish diseases and, published over 100 peer-reviewed articles.

He has more than 30 years of research experience including ~ 25 years of post-graduate teaching and mentoring, 8 years of administrative experience of heading the Research Division; Served as Dean (Academics), Dean (External relation), Chairman, Board of Studies, Member, Academic Council, Board of Management, Extension Council, Board of Examiners of the Fisheries University, and Member of the Management Committees of three national institutes. 

Dr Rajendran serves as one of the Editors of the journal VirusDisease (Springer) and Editorial Board Member, Fish & Shellfish Immunology Reports (Elsevier). 

His major research is on infectious diseases in aquaculture with a focus on developing diagnostics and understanding the host-pathogen interaction.