Vertical comprises four travel brands including Instant Holidays and Instant Breaks, the group's tour operating divisions. These sit alongside Your Holiday Booking and Holiday Elite, the group's dedicated homeworking divisions.
Together, the four Vertical brands currently achieve a combined £110 million annual turnover. Advantage called the group "a significant and sizeable player in the UK travel sector".
Advantage said the move further strengthens its position "as a leading supporter of independent travel businesses, providing them with a one-step solution to compete effectively in today's dynamic travel landscape".
Vertical was previously a member of Midcounties Co-operative.
Paul Nunn, Advantage's chief operating officer, hailed owner and chief executive of The Vertical Group, Peter Healey, and his team for the "exceptionally impressive business that has big ambitions for further growth".
"We are thrilled that they have chosen to partner with us to help support them achieve these strategic goals going forward," he said. "Their diverse portfolio and strong market position make them an ideal fit for our managed services model."
Healey, meanwhile, said the move was "an important strategic step for our business". "Joining Advantage Managed Services provides us with the flexibility, commercial strength and operational support we need to scale efficiently in what is an ever-changing market," he added.
"We see this new partnership as a major opportunity to take our business to the next level. AMS's proven experience and robust infrastructure will be invaluable as we focus on sustainable growth and continued innovation across all our divisions."