Haslam began his career at Pilot Corporation in 1976. In 1980, Haslam was named vice president of sales, development and operations. At that time, Pilot operated 100 convenience stores with annual fuel sales of about 125 million gallons. Pilot opened its first travel center in 1981, and by 1996 – the same year Haslam was named president and chief executive officer – the company operated 96 travel centers and 50 convenience stores and its total gallon sales had reached 1.2 billion. Pilot Corporation attained yet another milestone in 2001 when it joined with Marathon Ashland Petroleum LLC to form Pilot Travel Centers LLC.

In 2006, he served as Tennessee statewide campaign chair for the United States Senator Bob Corker and in 2012, he served as Statewide Finance Chairman for Tennessee Governor Bill Haslam, his brother. Haslam was inducted into the Junior Achievement of East Tennessee Business Hall of Fame in 2007, and in 2010, he was named a recipient of the Ernst & Young Entrepreneur Of The Year award for the Southeast region. In 2013, the University of Tennessee recognized Haslam with the Distinguished Alumnus Award. He is the co-founder of the Haslam Scholars Program for premier honor students at the University of Tennessee.

In 2008, Pilot Corporation announced that CVC Capital Partners had acquired 49.8% interest in Pilot Travel Centers LLC, facilitating the sale by Marathon Petroleum Company (formerly Marathon Ashland Petroleum) of its interest in Pilot Travel Centers. Pilot Corporation retained 50% ownership of Pilot Travel Centers LLC. In 2015, the Haslam family acquired all of CVC Capital Partners’ shares in the company. Pilot’s convenience store operations continue to be fully owned by Pilot Corporation. In 2010, Pilot Travel Centers LLC joined with Flying J Inc. In 2012, Pilot Flying J acquired Western Petroleum and the majority ownership of Maxum Petroleum and in 2012 formed Maxum Enterprises LLC, d/b/a Pilot Logistics Services. In 2014, Pilot Logistics Services merged with Thomas Petroleum to form Pilot Thomas Logistics. Pilot Flying J subsidiary Pilot Thomas Logistics is one of the fastest growing energy logistics companies in North America.

Haslam bought a minority interest in the Pittsburgh Steelers in 2008. In 2012, he reached an agreement with Browns owner Randy Lerner to purchase the franchise for $1 billion. The Browns were valued at $977 million in 2011 by Forbes magazine, 20th in the NFL. NFL rules prohibit ownership in multiple teams and so Haslam sold his interest in the Steelers. The Haslams’ purchase of the Browns was unanimously approved by the 32 teams in the NFL on October 12; the sale itself closed thirteen days later.

In April 2013, the FBI executed a search warrant and affidavit detailing a five-year fraud scheme by the Pilot Flying J chain. The company paid restitution to customers and agreed to pay a $92 million penalty pursuant to a Criminal Enforcement Agreement.

In late 2018, reports emerged that Haslam had purchased Major League Soccer club Columbus Crew SC from Anthony Precourt, who wanted to move the club to Austin, Texas. Haslam, along with his wife Dee and former team physician Pete Edwards, took over as owners on January 1, 2019, as a deal to purchase the club from Precourt was finalized.