Best of Suffolk was founded 15 years ago by husband and wife team Alex and Naomi Terry, who will stand down from their roles "to pursue other adventures".
The firm will operate as a standalone brand under the Sykes umbrella, supported by its team of nine, based near the Suffolk village of Framlingham.
Sykes said the deal would allow it to offer a broader range of properties and availability on the Suffolk cast, across the Brecks and "throughout Constable country".
“This deal will enable the business to continue to grow with those principles at its heart, while also allowing us to bring all that this beautiful part of the country to offer to a much broader audience of holidaymakers," said Graham Donoghue, Sykes chief executive.
Alex Terry added: “Stepping down after 15 years has been a difficult decision to make, but we are sure that our team, our property owners and our guests will be in good hands with Sykes Holiday Cottages.”