| Applibot Co., Ltd | Tokyo |
| Application Products Co., Ltd | Tokyo |
| Applied Design Analysis Corporation | Tokyo |
| Applied Technology Co., Ltd | Tokyo |
| ApplyNow Co., Ltd | Tokyo |
| Appmart Co., Ltd | Tokyo |
| APProg, Inc. | |
| Appui Co., Ltd | Osaka |
| APTO Corporation | |
| aptpod, Inc. | |
| AQ | Tokyo |
| AQTIA, Inc. | |
| Aqua Moon Systems Co., Ltd | Tokyo |
| Aquabit Corporation | Tokyo |
| Araya, Inc. | |
| Arc Communications, Inc. | Tokyo |
| Arc Corporation | Osaka |
| ARC Therapies | |
| Arcadia Knowledge Industry Co., Ltd | Tokyo |
| ARCALIS | |
| Archetype Corporation | Tokyo |
| Archetype Ventures Co., Ltd | Tokyo |
| Architectural Systems, Inc. | Tokyo |
| ArcJapan, Inc. | Tokyo |
| Arcnet Ltd | Hokkaido |
| Areanet Co., Ltd | Shizuoka |
| Aristo Japan Co., Ltd | Tochigi |
| ARK Co., Ltd | Tokyo |
| ArkEdge Space, Inc. | |
| ARKRAY Co., Ltd | Kyoto |
| ARKTAKE, Inc. | |
| ARM Ltd | Tokyo |
| Armonicos Co., Ltd | Shizuoka |
| Arrow Electronics Japan Co., Ltd | Tokyo |
| Arrow7 Co., Ltd | |
| Arsaga Partners, Inc. | |
| Art-Labo | Fukuoka |
| Artas Software Corporation | Tokyo |
| Arteria Networks Corporation | Tokyo |
| Arttech Co., Ltd | Fukuoka |
| AS-Accelerator | Saitama |
| Asahi Advertising Co., Ltd | Tokyo |
| ASAHI Agency | |
| Asahi Diamond Industrial Co., Ltd | Tokyo |
| Asahi Electronics Laboratory Co., Ltd | Osaka |
| Asahi Engineering Co., Ltd | |
| Asahi Intelligence Services Co., Ltd | Tokyo |
| Asahi Media Lab Ventures | Tokyo |
| Asahi Tech Co., Ltd | Osaka |
| Asahi University | |