Some of her successful films include Nidhanaya by Lester James Peiris, Siripala Saha Ranmenika by Amaranath Jayathilake, Eya Den Loku Lamayek and Bambaru Ewith by Dharmasena Pathiraja. She achieved a significant milestone in her artistic career with Sasara Chetana in 1984, where she became both its director and producer. She has directed two other films so far: Ahinsa in 1987 and Sthree in 1991.
She paired up with popular Tamil actor, Sivaji Ganeshan in Pilot Premnath in 1978.
Later on, she also worked in the television industry. Fonseka has won praise for her performance in Manalada Puthe Kiri Dunne, Pitagamkarayo, Kemmura, and Ambu Daruwo teledramas. She won the Sumathi Best Tele Actress Awards for her roles in Pitagamkarayo and Kemmura.