| IXXO Internet Solutions | North Rhine-Westphalia |
| J!German | North Rhine-Westphalia |
| J&F TGA GmbH | |
| j&s-soft GmbH | |
| J+D Software AG | Hesse |
| J3S GmbH | Hamburg |
| J5MEDIA GmbH | |
| JabRef | Baden-Württemberg |
| Jackmobile GmbH | Saxony |
| JackTiger | North Rhine-Westphalia |
| JackTools.Net UG (haftungsbeschränkt) | Bavaria |
| JACOB Elektronik GmbH | Baden-Württemberg |
| Jacobs University - Electrical and Computer Engineering | Bremen |
| Jade Hochschule | |
| Jaemacom GmbH | Berlin |
| JÄGER Management GmbH | Bavaria |
| Jakob-Kabel GmbH | Saarland |
| Jakota Design Group GmbH | Hesse |
| Jale Beteiligungs GmbH | |
| JAM Software GmbH | Rhineland-Palatinate |
| JAM Software GmbH | |
| Jamba! GmbH | Berlin |
| Jambit GmbH | Bavaria |
| Jamp Internetlösungen | Schleswig-Holstein |
| Jan Wohlfeil | |
| Janado GmbH | |
| Janich & Klass - Computertechnik GmbH | North Rhine-Westphalia |
| Janitza Electronics GmbH | Hesse |
| Jansass GmbH | Hamburg |
| Janßen Elektronik Service e.K. | Lower Saxony |
| Janz Tec AG | North Rhine-Westphalia |
| Jarltech Europe GmbH | Hesse |
| Java Logging Tools and Frameworks | Berlin |
| Java User Group Deutschland e.V. | Lower Saxony |
| Java User Group Dortmund | North Rhine-Westphalia |
| JavaScript Hero | |
| Javier Bórquez | Berlin |
| Jaysquared | |
| JB-Partners | |
| jBixbe | Saxony |
| JBSoftware | Hesse |
| jCatalog Software AG | |
| JCMB Beteiligungs GmbH | |
| JCON | |
| JDisc UG (haftungsbeschränkt) | Baden-Württemberg |
| JDS Sommer GmbH | Hesse |
| Jealouskid | |
| jedernet GmbH | |
| Jedox | Baden-Württemberg |
| Jelinek Computer | Hesse |