He plunged himself into active politics in 1951, joining the newly formed SLFP. After the inauguration of the SLFP in Kandy in 1951 by the late Prime Minister S.W.R.D. Bandaranaike, D.M. Jayaratne joined the party as its 13th member. Elected to Parliament from the Gampola electorate at the 1970 General Elections, he pursued his political career as a popular upcountry politician till his last days. Following the 2010 General Elections, he was appointed Prime Minister. The Ambuluwawa Multi-Cultural Centre was his brainchild.

The remains of the former Prime Minister were airlifted to the Parliamentary premises on Friday (November 22) where Members could pay their final respects from 1 pm to 3pm. Later the remains were brought to the parliamentary complex in a motorcade and received by Prime Minister Mahinda Rajapaksa, Speaker Karu Jayasuriya, Deputy Speaker Ananda Kumarasiri, Secretary General of Parliament Dhammika Dassanayake and Serjeant-at-Arms Narendra Fernando. UNP Leader Ranil Wickremesinghe was also present.

President Gotabaya Rajapaksa paid his final respects to the former Prime Minister on Friday evening in Parliament. Former President Maithripala Sirisena also paid his final respects. Later, the remains of the former Prime Minister were airlifted to his residence in Gampola.

The former Prime Minister passed away at the age of 88 while receiving treatment at a private hospital in Kandy. He was the father of three, including the former Deputy Minister of Mahaweli Development and Environment Anuradha Jayaratne.