Jinasada Niyathapala started his political career in 1946 through the United National Party's Youth movement.

In 1949 he held the position of Secretary General in the United National Party's youth movement.

The same year he was also assigned as United National Party's chief organiser of the Kotte electorate.

Jinadasa Niyathapala was also the editor-in-chief of United National Party's official publication Siyarata (Sinhala: සියරට).

He left the UNP and contested the 1977 general election from the Sri Lanka Freedom Party, but lost to Ananda Tissa de Alwis.