| iSupport Co., Ltd | Niigata |
| IT innovation Co., Ltd | Tokyo |
| IT Web Co., Ltd | Kanagawa |
| ITMaster | Tokyo |
| ITmedia, Inc. | Tokyo |
| ITO Corporation | |
| ITOCHU Techno-Solutions Corporation | Tokyo |
| ITOCHU Technology Ventures Co., Ltd | Tokyo |
| ITS Communications, Inc. | Kanagawa |
| IUK, Inc. | Tokyo |
| Iwagin Jigyo Souzou Capital Co., Ltd | |
| iWare Co., Ltd | Nagano |
| Iwate Biotechnology Research Center | |
| Iwate Medical University | |
| Iwate Prefectural University | |
| Iwate University | |
| IWATSU Electric Co., Ltd | Tokyo |
| IX Knowledge, Inc. | Tokyo |
| IXIT Corporation | Tokyo |
| iYell Co., Ltd | |
| Iyogin Capital Co., Ltd | |
| IzanagiGames Co., Ltd | Tokyo |
| Izumi Co., Ltd | Mie |
| Izumi Junior College | |
| J Sync Co., Ltd | Tokyo |
| J-Seed Ventures Co., Ltd | Tokyo |
| J-Startup | Tokyo |
| J-Startup City Project Japan | Tokyo |
| J-Tech Corporation Co., Ltd | Osaka |
| J. F. Oberlin University | |
| J.S.T. Mfg. Co., Ltd | |
| J:Drive Communications Co., Ltd | Tokyo |
| JAFCO Group Co., Ltd | Tokyo |
| Janis | Tokyo |
| JAOPS | |
| Japan Academy | |
| Japan Advanced Institute of Science and Technology | Tokyo |
| Japan Aerospace Exploration Agency | |
| Japan Agency for Marine-Earth Science and Technology | |
| Japan Antibiotics Research Association | |
| Japan Approvals Institute for Telecommunications Equipment | Tokyo |
| Japan Asia Investment Co., Ltd | |
| Japan Atomic Energy Agency | |
| Japan Automobile Research Institute | |
| Japan Aviation Electronics Industry Ltd | Tokyo |
| Japan BCG Laboratory | Tokyo |
| Japan Bio Products Co., Ltd | Tokyo |
| Japan Biological Informatics Consortium | Tokyo |
| Japan Blood Products Organization | Tokyo |
| Japan BSD Users Groups | Tokyo |