During a difficult political period, Dissanayake played a key role in reviving the Sri Lanka Freedom Party (SLFP) and was eventually appointed as the co-organizer of Kalawewa Constituency by SLFP Leader Sirimavo Bandaranaike. He was instrumental in several political victories, including the 1988 provincial council election and the 1989 general election, where three MPs from the Anuradhapura district were elected to Parliament.
Dissanayake was also a significant figure in the development of the SLFP, serving as the District party leader by 1994. He was awarded the post of Deputy Minister of Industrial Development and later, a senior ministership under President Chandrika Bandaranaike's government.
When establishing the Rajarata Medical College, required the creation of a teaching hospital, Chief Minister Berti Dissanayake mediated it and assigned the Anuradhapura General Hospital to the central government. He also supported transforming the Sri Lanka Institute of Advanced Technology into a Technical college.[7]
Despite facing opposition from within his political party for expressing his own ideologies, Berti was known as a strong figure who challenged the prevailing reactionary hegemony in the North Central and advocated for socialist ideals. During the 2005 presidential election, he actively worked to support Mahinda Rajapaksa's victory, with some organizational efforts in the North Central, Vavuniya, and Trincomalee areas.