| IMSA | Illinois Mathematics and Science Academy 
| Others |
| IMSA | Indiana Math and Science Academy
| Others |
| IMSA | Innovation Management System Advisor
| Others |
| IMSA | Installation Medical Support Activity
| Others |
| IMSA | Instrumentman Seaman Apprentice
| Others |
| IMSA | Insurance Marketplace Standards Association
| Others |
| IMSA | Intelligent Multimedia System For Automedication
| Others |
| IMSA | Interactive Multimedia System for Auto
| Others |
| IMSA | Interactive Multimedia System for Automobiles
| Others |
| IMSA | International Maritime Security Associates
| Others |
| IMSA | International Medical Spa Association
| Others |
| IMSA | International Medical Students Association
| Others |
| IMSA | International Memorialization Supply Association
| Others |
| IMSA | International Mind Sports Association
| Others |
| IMSA | International Montessori School of Albania
| Others |
| IMSA | International Motor Sports Association
| Others |
| IMSA | International Municipal Signal Association
| Others |
| IMSA | Internet Multimedia Systems And Applications
| Others |
| IMSA | Interscan Messaging Security Appliance
| Others |
| IMSA | Isuzu Motors South Africa
| Others |