- Abicorfin Oy - Abilitas Oy Ab
- Abin Baari - ABL Finland Oy / ABL-Laatat
- ABLE International Oy Ltd - Abloy Oy / Turku Sales Office
- Abloy Oy VingCard-korttilukitus - Aboa Engineering Oy
- Aboa Factum - Aboa Vetus & Ars Nova -museo
- Aboamed Oy - AB-Projektit Oy
- ABP-Service Oy - A-Briketti Oy
- Abrir Oy - AB-Service
- ABS-Hallintopalvelut Oy - absolute-North Ltd Oy
- Absolutext - Absusco Oy
- ABS-Vacum Oy - Abut Oy
- Abutilon Sp - AC Cranes Trading Oy
- AC Domector Oy - AC Pikahuolto Oy
- AC Sport - Academic Work Suomi Oy Ab
- Academica Information Oy - Acalle Tmi
- Acaman Oy Ab - A-Carpet Oy
- Acartia Avoin yhtiö - Ac-Call F:ma
- Accanto Systems Oy - Accent Audio Visual Production
- Accent Finland Oy - Access Advertising Oy
- Access Advertising Oy - Accon Oy
- ACCOnline Finland Oy - Account Team Service Oy
- Accountia Consulting Oy - Accrys Oy
- Accu Plaza Oy - Ace Henkilöstöpalvelut Oy