By 1966 Gillett became the manager and partner of the Miami Dolphins. He eventually bought a 20 percent interest of the Dolphins NFL franchise for $1 million. Two years later, he sold his share for $3 million to buy the Harlem Globetrotters and later started a national radio group called Globetrotters Communications. By the late seventies, Gillett started his own radio and television organisation, Gillett Communications, later owning many affiliates including CBS.
Throughout the 1980s, Gillett acquired several organisations including Nashville's WSM television station, Storer Broadcasting, Vail and Beaver Creek Ski Resorts. By the mid 1990's, he formed Booth Creek Ski Holdings, building several ski resorts, in New Hampshire, California and Washington.
At the beginning of the century, Gillett's business interests expanded to sports, purchasing 80 per cent interest in NHL Montreal Canadian and its home arena (Molson Centre) for a whopping $185 million. He also purchased several NASCAR teams. In 2007, Gillett and business partner Tom Hicks became owners of Liverpool F.C. By 2010, Gillett lost ownership of Liverpool F.C.
