He entered parliament from Medawachchiya Electorate in 1947 when then Ceylon held its first parliamentary elections.

Bandaranaike was biding his time after he had resigned from UNP and making plans for the future with his nascent Sri Lanka Freedom Party and offered a place to Maithripala Senanayake, who was then an Independent MP in Parliament.

Senanayake has held many cabinet portfolios and has been Acting Prime Minister 19 times, Leader of the House, Chief Government Whip, and Deputy Leader of the Opposition at various times.

In the realm of Foreign Affairs, Maithripala Senanayake has also played a major role, when the then Prime Minister Mrs. Sirimavo Bandaranaike was President of the Non-aligned Movement, he led the Sri Lanka delegation to the 5th Summit of the Non-Aligned Movement held in Colombo.

However he was appointed the governor of the North Central Province in the same year which he held until his death.