| Diea Design | Seoul |
| Digent | Seoul |
| Digiatom Co., Ltd | Seoul |
| Diquest | Seoul |
| Direct Hosting | Seoul |
| DNA Link, Inc. | Seoul |
| Dnotitia | |
| DNSOFT Co., Ltd | Seoul |
| dob Studio, Inc. | Seoul |
| Dohands Corporation | |
| domain21.org, Inc. | Seoul |
| Domainbank | Seoul |
| Domainca | Seoul |
| Dong Seoul University | |
| Dong-A ST | Seoul |
| Dong-a University | |
| Dong-Ah Institute of Media and Arts | |
| Dong-eui Institute of Technology | |
| Dong-eui University | |
| Donga University of Health | |
| Dongbang Culture University | |
| Dongduk Women's University | |
| Donggang University | |
| Dongguk University | |
| Dongnam Health University | |
| Dongseo University | |
| Dongshin University | |
| Dongwon Parts | Gyeonggi |
| Dongwoon Anatech | Seoul |
| Dongyang Mirae University | Seoul |
| Dongyang University | |
| Doomoolmori Co., Ltd | Seoul |
| Doople Incorporation | Gyeonggi |
| Doosan Corporation Electro-Materials | Seoul |
| Doowon Technical University | |
| Doregi | Seoul |
| Dot Incorporation | Seoul |
| Dotname Korea Corporation | Seoul |
| DoubleMe | Seoul |
| DoubleU Games Co., Ltd | Seoul |
| Dowooinsys | North Chungcheong |
| Dragonfly GF Co., Ltd | Seoul |
| DREAMPLUS | Seoul |
| DrimSys, Inc. | Seoul |
| DSC Investment | Seoul |
| DSLAB Global | Seoul |
| DSTechno Co., Ltd | Gyeonggi |
| DuChemBio Co, Ltd | |
| Duksan Techopia Co., Ltd | South Chungcheong |
| Duksung Women's University | |