| Diseño y software Windsock | A Coruña |
| Diseon.com | Valencia |
| Disertum | Barcelona |
| 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 |
| 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 |
| Dos Espacios | Pontevedra |
| DOS Software, S.A. | Barcelona |
| Dost | Barcelona |
| DOVALO Informática | Las Palmas |
| Dozen Investments PFP, S.L. | Barcelona |
| DPIProducts, S.L.U. | Madrid |
| DQ System, S.L. | Madrid |
| Dracnet Projects | Barcelona |
| DraperB1 | Valencia |
| Dreamsite | Madrid |
| Dribba Development & Consulting, S.L. | Barcelona |
| Drive REVEL, S.L. | Madrid |
| DS Data Systems Iberia, S.A. | Madrid |
| DSTnet TPV | Cádiz |
| Duacode | A Coruña |
| Duero Imagen | Burgos |
| Duocom Europe, S.L. | Las Palmas |