During the 1970s, Wijewardene worked as an expert on tropical farming systems with the UN Food and Agriculture Organisation (FAO) and the World Bank.

He held appointments such as Chairman of the Tea Research Board, Commissioner Sri Lanka Inventors Commission and was a member of public sector bodies concerned with agriculture, science and technology.

In an early attempt to mechanise farm labour during the Green Revolution, it was manufactured and marketed worldwide by the Landmaster company.

[3] He promoted a soil conservation technique called Sloping Agricultural Land Technology (SALT),[4] originally developed in the Philippines.

[5] After returning to Sri Lanka in 1980, Wijewardene spent the rest of his years researching and promoting ecologically sustainable agriculture and renewable energy technologies.

He experimented with rain-fed farming and agroforestry methods on his coconut estate in Kakkapalliya, in Sri Lanka's Intermediate Zone.

Wijewardene engaged in the water sports of rowing and sailing and represented Sri Lanka in international competitive events.

Anoma is an artist, and Mandy is married to prominent Sri Lankan author Suresh Mudannayake (known as Ashok Ferrey).