Wijeyeratne was instrumental in obtaining rights for Sri Lankan lawyers to wear the national dress to courts.

During this time, he expressed strong public opinion for the formation of a separate Foreign Ministry in Sri Lanka.

As Additional Secretary, Wijeyeratne placed strong emphasis on the Sri Lankan national identity within the foreign service.

He brought a Sinhalese and Tamil oriented dimension to the Foreign Office, recruiting locally educated youth to nurture Sri Lanka's identity in missions abroad.

He also proposed the initiation of a Diploma course in Diplomacy at an institute of foreign affairs that would be affiliated with the University of Sri Lanka, providing training opportunities to hopeful diplomats.

During the late 1970s, Tissa Wijeyeratne being a firm believer in uplifting the life of rural communities in Sri Lanka, ventured into finance.

His deep belief in the economic philosophy of British economist E. F. Schumacher lent the company its motto "Small is Beautiful".

The company commenced business in 1979 under the name of Sinhaputhra Agricultural and Industrial Finance Ltd. and focused initially on providing vehicles to rural areas for the transport of their produce to markets.

During his tenure, he also helped promote the establishment of the Sri Lanka Institute of Credit Management to strengthen the industry.