It follows the acquisition of five-office ergo by Edelman in December, and Golin's entry into the market in a joint venture with a fellow Interpublic Group agency, announced in April.
Higher Ground will lose its name, but retain its founders – Martina Müller and Vivian Dadamio will be senior vice-presidents leading new Allison+Partners offices in Berlin and Munich respectively.
The pair set up the agency in 2010, and it has seven staff. It has been acquired outright by Allison+Partners. Terms of the deal were not disclosed.
Müller previously worked for Porter Novelli, and Waggener Edstrom – now WE – prior to that. Dadamio also worked for Waggener Edstrom, later moving to Hill+Knowlton Strategies.
Higher Ground had collaborated with Allison+Partners on numerous projects in recent years for Allison+Partners clients such as Public Interest Registry, Rally Software and RetailMeNot. Higher Ground's website lists clients including Citrix, McAfee, T Mobile and SAP.
Dadamio said Allison+Partner's "unique, one global P+L structure" provided a "true benefit to clients" and that it placed a high value on "maintaining a positive work culture".
She and Müller will report to Matthew Della Croce, president of the agency's European operation and its global corporate practice.
Della Croce said: "As one of the largest economies in the world, Germany has always been an important market for our clients. Martina and Vivian have already been providing in-market support to a number of our clients, and will continue to be invaluable assets as we diversify our capabilities and grow our client base more broadly across Europe.
San Francisco-headquarter Allison+Partners is the world's 44th largest PR firm, according to the PRWeek Global Agency Business Report 2016. In its profile for the GABR, the firm's CEO named Germany as a target for global expansion, alongside Amsterdam, and Indonesia.