The deal is for an initial sum of up to £5.4 million (HK$63.5 million), with a further payment to be made in relation to the net assets of Widnell upon delivery.
Cyril Sweett made the acquisition through its wholly-owned subsidiary Cyril Sweett International.
Hong Kong-based Widnell employs around 400 people in its subsidiaries across China and Macau. The company provides consultancy services to private and public sector clients for construction work.
Widnell declared profits after tax of HK$16.6 million for the year to February 2010, on a turnover of HK$106.4 million.
AIM-listed Cyril Sweett was founded in 1928 and has 35 offices across the UK and the rest of the world. The construction and property consultancy provides services including project management and building surveying.
Dean Webster, CEO of Cyril Sweett, says: ‘The group’s strategy is to diversify the business across territories and sectors that are forecast to grow, whilst consolidating our presence where the business has a market-leading position.’