Being an active worker in the Communist Party of India (Marxist), he assumed the role of being the secretary of Seethathodu Local Committee at an early age.
He is currently the district committee member of CPI(M) in Pathanamthitta and the Kerala state vice president of Democratic Youth Federation of India.
In 2010, he won the Seethathodu Grama Panchayat election after defeating the Indian National Congress in highest margin recorded in Kerala.
[6] Representing CPI(M) in the Left Democratic Front, K. U. Jenish Kumar won from Konni constituency for the 2019 Kerala legislative assembly by-election held on 21 October 2019.
[9] Both K. U. Jenish Kumar and district collector P. B. Nooh IAS received public praise for bringing food items directly to Avanippara Girijan Colony as part of the MLA's Kaithangu scheme after trekking 3 km (1.9 mi) in forest.