In 2008, four firms—Colliers Turley Martin Tucker in the Central U.S.; Colliers Pinkard in Baltimore, Raleigh and Charlotte; Cassidy & Pinkard Colliers in Washington, DC; and Colliers ABR in New York City—merged to form a joint holding company. The four firms, part of the Colliers International network, continued to operate under their names and brands in each market, but consolidated leadership, with Mark Burkhart of Colliers Turley Martin Tucker becoming CEO of the holding company.
In early 2010, FirstService Corp., parent company of Colliers International, merged the U.S. and global operations of Colliers and FirstService Real Estate Advisors. That same year, the holding company of Colliers Turley Martin Tucker, Colliers Pinkard, Cassidy & Pinkard Colliers and Colliers ABR – and Colliers Houston & Co. of New Jersey, NAI affiliate BT Commercial in Northern California, Grubb & Ellis BRE Commercial in San Diego and Phoenix – formed a new national company under the brand of Cassidy Turley. Soon after, CPS CORFAC in Santa Clara, CA joined Cassidy Turley as Cassidy Turley CPS.
During 2010 and 2011 Cassidy Turley added offices in Milwaukee, WI Denver, CO, Louisville, KY and Dallas and Houston, TX. In 2010, the firm formed an international partnership with GVA to provide services outside the U.S.
On September 6, 2011, Cassidy Turley completed its acquisition of the brokerage and property management business lines of Carter, a commercial real estate services firm headquartered in Atlanta. On September 15, 2011, Cassidy Turley announced its acquisition of FHO Partners, a commercial real estate brokerage and advisory firm in Boston.
Cassidy Turley opened its first Los Angeles office on April 30, 2012, when it hired four brokers from Transwestern to lead Cassidy Turley's growth in the city.
On Oct. 5, 2012, Cassidy Turley's board of directors unanimously elected Joseph Stettinius Jr. as the company's new CEO, replacing Mark Burkhart, who now serves as an advisor to the company. With Stettinius' election, Cassidy Turley effectively moved its national headquarters to Washington, DC, where he is based.
On Jan. 2, 2013, Cassidy Turley expanded its Florida presence by completing a merger with Tampa-based CLW Real Estate Service Group. The following week, Cassidy Turley promoted Michael Kamm, based in San Francisco, to president.
According to an article in the April 2013 issue of Real Estate Forum, Cassidy Turley ranked No. 5 on the 2013 edition of Lipsey Co.'s annual survey of the Top 25 brands in commercial real estate. 
In July 2013, the company announced plans to open a new office in downtown St. Louis initially with 30 employees in October, adding to the seven already in the region. It has 800 employees in the region presently with its main St. Louis office in the Clayton, Missouri suburb.
In September 2014, the company announced that it has entered into an agreement with an affiliate of DTZ Investment Holdings, backed by TPG, PAG Asia Capital and Ontario Teachers’ Pension Plan (the Consortium that agreed to acquire DTZ), to sell 100% of the equity interests of Cassidy Turley. The agreement is subject to customary closing conditions and is dependent on Cassidy Turley’s combination with the operations of DTZ Group (DTZ) to create a global, full-service commercial real estate services company. The Consortium’s acquisition of DTZ is currently scheduled to close in early November 2014. The acquisition of Cassidy Turley is expected to close December 31, 2014.