| International Pacific University | |
| International Research Center for Japanese Studies | |
| International Society for Mathematical Sciences | Osaka |
| International Superconductivity Technology Center | |
| International Systems Research Co., Ltd | Tokyo |
| International University of Health and Welfare | |
| International University of Japan | |
| International University of Kagoshima | |
| Internet Association Japan | Tokyo |
| Internet Initiative Japan, Inc. | Tokyo |
| Internet Intiative Japan, Inc. | Tokyo |
| Internet JAH | Tokyo |
| Internet Kani | Tokyo |
| Internet Kurume | Tokyo |
| Internet Multifeed Co., Ltd | Tokyo |
| Internet Owari Co., Ltd | Tokyo |
| Internet-TV Corporation | Tokyo |
| Interprotein Corporation | |
| InterQuest Co., Ltd | Tokyo |
| InterRobot Co., Ltd | Okayama |
| Interspace Co., Ltd | Tokyo |
| Interstellar Technologies Co., Ltd | Hokkaido |
| Interwired Co., Ltd | Tokyo |
| Interwork Corporation | Tokyo |
| Intimate Merger Co., Ltd | Tokyo |
| Invoice, Inc. | Tokyo |
| ION Software, Inc. | Tokyo |
| Ion Technology Center Co., Ltd | Osaka |
| Iosys Co., Ltd | Tokyo |
| IoT- EX Co., Ltd | Tokyo |
| IP Cube Co., Ltd | Tokyo |
| IP Innovations | Tokyo |
| iPark Institute Co., Ltd | |
| IPC Co., Ltd | Tokyo |
| IREP Co., Ltd | Tokyo |
| iRepairs, Inc. | |
| IRISO Electronics Co., Ltd | Kanagawa |
| iROBOTICS Co., Ltd | Tokyo |
| Iryo Sosei University | |
| Isahya Computer College | Tokyo |
| ISB Corporation | Tokyo |
| Ishikawa Computer Center | Tokyo |
| Ishikawa Prefectural University | |
| Ishikawa Prefecturla Nursing University | |
| ISI Corporation | Tokyo |
| Isoplotec Corporation | Tokyo |
| ispace Co., Ltd | Tokyo |
| iSQUARE Co., Ltd | Tokyo |
| IssueHunt K.K. | |
| IST-Software Co., Ltd | Tokyo |