Tull grew up in Endwell, New York, the son of a dental hygienist single mother. As a youth, Tull was an athlete, playing baseball and playing football, earning a football scholarship. Tull graduated from nearby Hamilton College in 1992. After college, Tull abandoned plans to become a Lawyer and instead went into Business, starting a chain of laundromats. Among his distinguishing innovations was different prices according to demand at different times of day. Tull went into the field of financing, buying and selling several tax and accounting offices. In the private equity Business, Tull rose to President of Convex Group and later as the Chief of Operations of Tax Services of America. His firm invested in entertainment, where Tull began to learn the entertainment Business. After discussing the potential of private equity with a film executive in 2003, Tull quit Convex, raising $600 million in equity to Finance movies under the Legendary Pictures banner. The company entered into a partnership in 2005 with Warner Bros. to jointly Finance and produce films. In 2009, Tull became the majority shareholder of Legendary, in a buyout of the original Investors. The Warner deal was followed by a similar deal with Universal Studios in 2013. He also helped produce the film Blackhat.
Tull is a member of the board of trustees for the American Film Institute, Carnegie Mellon University, and the San Diego Zoo. In 2009, Tull became a part-owner of the Pittsburgh Steelers football team. Tull had been a fan of the Steelers since age four, watching the Steelers take on the Minnesota Vikings in Super Bowl IX.