| Danbit Systems | Masovian |
| DANKA Polska Sp. z o.o. | Masovian |
| Danmar Computers | Subcarpathian |
| Darpol S.C. | Lubusz |
| Dasoft Sp. z o.o. | |
| Data Force Group Sp. z o.o. | |
| Data Force Group Sp. z o.o. Sp. k. | Masovian |
| Data Lab | Greater Poland |
| Data Soft | Lublin |
| Data Space Sp. z o.o. | |
| Data.rocks | |
| Database Consulting Sp. z o.o. | |
| databroker S.A. | |
| DataCommunity | |
| Datacomp IT Sp. z o.o. | |
| DataConsult | |
| DataContact | |
| Dataedo | Pomeranian |
| DataMax Recovery | Masovian |
| DataMiners Sp. z o.o. | |
| Dataplace.ai | |
| DataSystem | Silesian |
| Datel Sp. z o.o. | Greater Poland |
| DayOne | |
| DBB Software | |
| DC House | |
| dcs.pl Sp. z o.o. | Masovian |
| DDI Development | |
| Dealavo | |
| Dealme Sp. z o.o. | |
| Decsoft S.A. | Masovian |
| Deepflare | |
| DeerTech | |
| Delante Marketing Sp. z o.o. | |
| DeliaSoft Sp. z o.o. | |
| Deltologic | |
| DEM Interactive | |
| Demoboost Sp. z o.o. | |
| Dempan Sp. z o.o. | Lesser Poland |
| Department of Web | |
| Depcore | |
| Dercom | Masovian |
| Derkom Sp. J. | Lublin |
| Design Joomla | Pomeranian |
| Design Park | Silesian |
| DesignCart.pl | |
| desire24.com | Silesian |
| DESK.WORKS Sp. z o.o. | Greater Poland |
| Deskset Software Sp. z o.o. | |
| DeSmart Sp. z o.o. | |