| PC Koubou | Tokyo |
| PC Life | Tokyo |
| PC-Wrap | Osaka |
| Pcagogo | Tokyo |
| PCC Co., Ltd | Tokyo |
| PChands | Tokyo |
| PD AeroSpace Co., Ltd | Aichi |
| Pegasys, Inc. | Tokyo |
| Pentacom.jp | Tokyo |
| Pentax Medical | Tokyo |
| Peptide Institute Co., Ltd | Osaka |
| PeptiDream Co., Ltd | Kanagawa |
| Peritech International Co., Ltd | Tokyo |
| Perl Script Laboratory | Tokyo |
| Perseus Proteomics, Inc. | |
| Persol Cross Technology Co., Ltd | Tokyo |
| Personal Media Corporation | Tokyo |
| PHC Holdings Corporation | Tokyo |
| Phoenix Club Internet Service | Tokyo |
| Phoenix Technology | Tokyo |
| PhoenixBio Co., Ltd | Hiroshima |
| Phone Appli, Inc. | |
| PicoLix | Tokyo |
| Pikolab Co., Ltd | Fukuoka |
| Pinmicro Co., Ltd | Tokyo |
| Pioneer Corporation | Tokyo |
| Pioneer Corporation | |
| PIONICS Co., Ltd | |
| Pipon Co., Ltd | Tokyo |
| Pivot Co., Ltd | Tokyo |
| Pixel Companyz Co., Ltd | Tokyo |
| Pixie Dust Technologies Co., Ltd | Tokyo |
| PKSHA Technology, Inc. | |
| Plaid Co., Ltd | Tokyo |
| PLAN-B Co., Ltd | Osaka |
| Planetaria Co., Ltd | Tokyo |
| Planex Communications, Inc. | Tokyo |
| Planning Village Corporation | Tokyo |
| Playing Network Co., Ltd | Tokyo |
| Plum Five Co., Ltd | Kanagawa |
| Plus1 Co., Ltd | Tokyo |
| PMT Corporation | |
| PocketRD, Inc. | |
| Poetics, Inc. | |
| Polaris Co., Ltd | Ibaraki |
| Ponde Tech Co., Ltd | Osaka |
| POPORO Internet Service | Tokyo |
| Portwell Japan, Inc. | |
| PPDGen | Tokyo |
| PRAGE, Inc. | Tokyo |