TCI
- IEEE 802.1Q
- Tall Clubs International
- Taoist Church of Italy
- Target controlled infusion
- Tele-Communications Inc.
- Telecommunication Company of Iran
- Televisione Cristiana in Italia
- Telus Communications Inc.
- Temperament and Character Inventory
- Tenerife Airport (disambiguation)
- Tennessee Coal, Iron and Railroad Company
- Texas Correctional Industries
- The Children's Investment Fund Management
- Theme-centered interaction
- Therapeutic Crisis Intervention
- Thistletown Collegiate Institute
- Tokyo Chemical Industry
- Touring Club Italiano
- Toyota Canada Inc.
- Transport Corporation of India
- Transportation and Climate Initiative
- Turks and Caicos Islands