Educated at Nalanda College, Mahanama is currently a business development manager at Air Tiger Express. His most outstanding achievement as a cricketer was establishing a new world record for the highest partnership for any wicket in Test cricket with Sanath Jayasuriya. The pair put on 576 for the second wicket, batting over two full days. Mahanama's contribution was 225.
At school, Mahanama won the 'Observer' Most Popular Schoolboy Cricketer of the Year award in 1983-84 and also the Most Outstanding Schoolboy Cricketer of the Year and Best Batsman and Best Fielder awards.
He was the youngest cricketer to play division I cricket in Sri Lanka when he appeared for Bloomfield at the age of 13 in 1980, the year the club emerged champions. He was captain of Bloomfield for three years from 1995 to 1997.
He was a member of the Sri Lanka team that won the World Cup in 1996 and has represented his country in 52 Tests and 195 one-day internationals. Rated one of the best fielders in the game, he has held 57 catches in Tests and 100 in one-day internationals. Was voted one of the Five Cricketers of the Year by Indian Cricket in 1997.