| jemo-webdesign | Bavaria |
| Jena-Optronik GmbH | |
| Jenaer Antriebstechnik GmbH | Thuringia |
| Jenaer Leiterplatten GmbH | Thuringia |
| JENDATA Computersysteme GmbH | Thuringia |
| Jenetic GmbH | |
| Jenny Hofer Print- & WebDesign | Hamburg |
| Jenoptik AG | Thuringia |
| Jensen Software Systems | Schleswig-Holstein |
| JENTECH Datensysteme AG | Thuringia |
| JENTIS GmbH | |
| Jericho Datentechnik GmbH | Rhineland-Palatinate |
| JERRA GmbH | Saarland |
| Jescali GmbH | North Rhine-Westphalia |
| Jeske EDV-Service | Hesse |
| JessenLenz | Schleswig-Holstein |
| JET Consult GmbH & Co. KG | |
| JET-Electronics GmbH | Bavaria |
| JET-Software GmbH | Hesse |
| Jetztwerk | Hamburg |
| Jeweils verantwortlich für Inhalte und Redaktion sind: Forschungsgruppe Wahlen e.V. | |
| JFK089 | |
| JGoodies | Schleswig-Holstein |
| jimago Gesellschaft zur Vermarktung von Fotokunst mbH | |
| Jimdo GmbH | Hamburg |
| Jina AI | |
| Jinx Software | Bavaria |
| JIOWA Business Solutions GmbH | Hesse |
| JIT Electronic GmbH | Bavaria |
| Jiva Materials | |
| JJP Management Consult | |
| JK Computer Systeme GmbH | North Rhine-Westphalia |
| JKBB | Lower Saxony |
| JKS Leiterplatten GmbH | Lower Saxony |
| JL Software | Bavaria |
| JLCPCB | |
| JLSoft EDV-Dienstleistungen | Baden-Württemberg |
| JMC Jens Moeller Consulting GmbH | Bavaria |
| JMMG Communications | North Rhine-Westphalia |
| JO Software Engineering GmbH | Baden-Württemberg |
| Jo-Soft IT-Security GmbH | North Rhine-Westphalia |
| Joachim Tamcke Idee+Konzept - EDV Beratung | |
| Job Ambition GmbH | |
| jobaTEC GmbH | |
| Joblift GmbH | |
| JobMatch.me GmbH | |
| Jobo | |
| JOBO International GmbH | North Rhine-Westphalia |
| Jobpal | Berlin |
| Jobpool GmbH | |