| Dinartis | Alicante |
| Dinbeat | Barcelona |
| Dinsa | Madrid |
| Dinube Mobile Payments & Loyalty, S.L. | Barcelona |
| Dioxinet | Madrid |
| Dipolerifd | Barcelona |
| Direcline Software | Barcelona |
| Direct Telecom, S.L. | Santa Cruz de Tenerife |
| Diseñando Online, S.L. | Madrid |
| Diseño Páginas Web Yá | Barcelona |
| Diseño web | Sevilla |
| Diseño Web Toledo | Toledo |
| Diseño y software Windsock | A Coruña |
| Diseñoideas | |
| Diseon.com | Valencia |
| Disertum | Barcelona |
| DISITBiotech | |
| Diskover Co. | Madrid |
| DISMON Electrónica, S.L. | Biscay |
| Dismuntel S.a.l. | Valencia |
| Disruptivos | Málaga |
| Dissenart | Valencia |
| Distintiva S.Coop. | Álava |
| Distrito K | A Coruña |
| Ditecom Design, S.L. | Madrid |
| Dive | Madrid |
| Divilo | Madrid |
| Divisa IT | Valladolid |
| DM Dima | Madrid |
| DMD Electron, S.L. | Santa Cruz de Tenerife |
| dmELECT | Almería |
| DMI Computer, S.A. | Madrid |
| DN Electronic, S.L. | Barcelona |
| DNAverse | Madrid |
| Dnest Digital Agency | |
| DNOiSE | Madrid |
| Dobecure, S.L. | Madrid |
| Doblespacio | A Coruña |
| Dobuss | |
| Doctores del PC | Madrid |
| Docuten Tech, S.L. | A Coruña |
| Dog Comunicación, S.L. | Madrid |
| Domestic Data Streamers | |
| Dominios en venta | Madrid |
| Dominios Plus | Madrid |
| Dommia | Barcelona |
| DonDominio | Balearic Islands |
| Doominio.com (Ezynic, S.L.) | Asturias |
| Doowebs Dev, S.L. | |
| Dos Espacios | Pontevedra |