The seven-figure deal effectively brings three companies under one roof - UP, Tide Studio and Hampton - allowing the enlarged group to offer services ranging from human resources, recruitment and training to brand consultancy, digital and graphic design, and events management.
UP expects the combined group to turn over £5 million in the first 12 months, which would mark a £750,000 hike on the same period last year.
It also plans to hire a further member of staff before the end of the year, adding to its existing 40-strong workforce.
Each of the three companies will retain their individual trading identities.
UP managing director Campbell Urquhart said: "We genuinely see this deal as equally beneficial for all three businesses involved.
"We are a much stronger entity as a result of this transaction, offering our clients easier, and more efficient, access to a wide range of diverse, and yet related, services."
UP and Hampton Associates, which have worked together for more than 15 years, opened talks over the deal in September. This came after UP had completed its acquisition of DEER Digital, which has since been rebranded Tide Studio.
Hampton managing director Mike Hampton will remain with the business as a non-executive director, with Hampton's Scott Hunter becoming creative director at the enlarged group.