The acquisition went through last night after DTZ Holdings was pushed into administration.
Ernst & Young, which handled the deal, said the business will continue to operate as a going concern and move will safeguard around 4,700 jobs.
DTZ selected UGL as its preferred bidder last month after its biggest shareholder Saint George Participations pulled out of a planned takeover.
The company posted annual pre-tax losses of £3.4 million in July and closed its economic development and regeneration department earlier this year.
It has 13 offices in the UK, six of which have planning teams. As of September 2010, DTZ had 24 chartered planners with half of them working in the main London office, according to Planning’s 2010 annual consultancy survey. The consultancy's planning fee income for 2009/10 was £4.5 million, according to the survey.
The company also operates across Asia, Europe, Middle East and the United States.
UGL said the combined property services business will have around 53,000 employees, operating in 240 offices in 43 countries, making it one of the largest companies in the global property services sector.
DTZ chief executive John Forrester said the companies are an exceptional fit and will provide enormous benefits to its clients and employees.