Jacobs, 31, spent two years at Wasps between 2009-2011 before stints with the Japanese side Kyuden Voltex and the Force.
Wasps turned to Jacobs, a former Australia A international, after Welsh centre Lee Thomas was forced to retire because of an Achilles injury.
Director of rugby Dai Young said: "Ben's experience will be a big asset for us this season.
"Losing Lee Thomas to retirement was a real disappointment for both ourselves and the players recently but Ben will come into that midfield mix and do a very good job for us.
"He knows the club inside out and was very keen to come back here, so we're looking forward to him joining up with us again."
- Sports & Recreation
- Kyuden Voltex