He attended D. S. Senanayake College, Colombo for his secondary education, where he passed the GCE A/L examination in 1988 and won a scholarship from the Australian government to study for a degree in computer science at Monash University.

[citation needed] In 2007, he was appointed as the chairman of the Central Environmental Authority by the President Mahinda Rajapaksa.

Gammanpila also served as a member of the All-Party Representatives Committee appointed by the President to resolve the North-East crisis in August of that year.

[citation needed] In 2009, he voluntarily resigned as chairman of the Central Environmental Authority to contest for the Western Provincial Council.

His latest book is Mahinda Sulagin Gotabhishekayata, which features the behind-the-scenes story of Gotabhaya Rajapaksa entry into politics and power.