- Philatelic & Numismatic Society
- Robotics Club
- Yoga Club
- Library Club
- Environmental Club
- College Magazine
- Chamber Orchestra
- Cinema Society
- Astronomy Club
- Aquarium Club
- Scuba Diving Unit
- Culinary Arts Society
- Aeronautical Societya
- Junior Science & Technology
- Histoarcheo Club
- Geography Society
- Gavel Club
- Student Christian Movement
- English Lit & Debating Society
- Radio Club
- Junior Maths Society
- Road Safety Patrol
- Sinhala Literary & Debating Society
- Seylan Bank Students’ Savings Unit
- HNB Students’ Savings Unit
- Kennel Club
- Buddhist Students’ Association
- Junior English Lit & Debating Society
- Art Club
- Spelling Union
- Carnatic Orchestra
- Canto Perpetua Choir
- Western Band
- Tamil Drama Society
- Hewisi Band
- English Drama Society
- Photographic Club
- Society for Social Work & Welfare
- ICT Society
- Senior Environmental Club
- Hindu Students’ Union
- Political Science Society
- Red Cross Society
- Association of Innovation and Design
- Islamic Society
- Association of Science and Technology
- Quiz Club
- Automobile Club
- Cubing Society
- Health Club
- Tamil Literary and Debating Society
- Wildlife Society
- Thomian Union
- Commerce Society
- Interact Club
- The Ternion
- Classical Music Association
- Media Unit
- Productive Citizenship Society
- United Nations Club
Cubing Society
Cubing helps improve memory & problem solving skills, makes one’s reflexes faster and keeps the mind active. Thus, the Cubing Society of S. Thomas’ College was established during the Michaelmas Term of 2017 to encourage young cubing enthusiasts to take up speed cubing as a hobby. Since then, we have been teaching the basics of speed cubing to many a young Thomians, and organize informal intra-club matches between the members to improve their skills.