- Ace High - Aceguard Trading Oy
- Ace-Gun Oy - Acephalus Consulting
- Acepoint Oy - AC-Express Oy
- ACF Air Clean Oy - Achilleus
- Achmea Schadeverzekeringen N. V. - Ackermen Oy
- AC-Kiinteistö Oy - ACME Limo Service
- ACME Service - ACN Sponsors Oy
- ACO Hud Nordic Ab - Aconi Oy
- Aconitum - AC-Plan
- AC-Puusta Ky - ACS Finland
- AC-Sanafor Oy - Actelion Pharmaceuticals Sverige Ab filial Finland
- Actic Kuntokeskus & Uinti - Action Lähetit
- Action Machines Oy - Action Show Team Oy
- Action Sports GmbH - Activa AC
- Activa Invest Oy - Active Garden / Arctic Finland House LTD OY
- Active group - Active Process Tmi
- Active Promoting Finland Oy Ab - Activen Oy
- ActiveSoft Oy - Actorit Oy
- Actor's in Scandinavia Ab - Acu Rennox
- Acu-Elektro Ab - ACUTEHook Oy Ltd
- A-Cuter Oy - AD Autokorjaamo Beneten
- AD Autokorjaamo Citix - AD Autokorjaamo Maxiauto
- AD Autokorjaamo MBA - AD Autotalo Kiukas