Gallogly joined the Phillips Petroleum Company in 1980. He worked in a variety of legal, financial and operational positions including international assignments in Norway. He was appointed vice president of plastics, vice president of olefins and polyolefins and later senior vice president of chemicals and plastics. Gallogly has held executive positions with ConocoPhillips, ChevronPhillips and Phillips Petroleum. Phillips Petroleum Corp. and Chevron Corp. combined to form Chevron Phillips Chemical as a joint venture in June 2000. Gallogly became the inaugural president and chief executive officer of Chevron Phillips Chemical, one of the world's top producers of olefins and polyolefins, remaining there until 2006. In 2002, Conoco Inc. and Phillips Petroleum merged to form ConocoPhillips, based in Houston, Texas. In 2006, Gallogly joined ConocoPhillips as executive vice president of refining, marketing and transportation and later as executive vice president of exploration and production. Gallogly became the chief executive officer of LyondellBasell in Houston, Texas in 2009, succeeding Volker Trautz as part of a reorganization following U.S. bankruptcy court proceedings. Gallogly guided the company out of Chapter 11 bankruptcy and successfully repositioned it as one of the world's largest refining companies and makers of polymers and petrochemicals. Gallogly formally retired as CEO of LyondellBasell in January 2015. As of February 5, 2015, he was appointed as a director of DuPont Gallogly formerly served on the Board of Directors for Continental Resources. He also served on the University Cancer Foundation Board of Visitors at the University of Texas M. D. Anderson Cancer Center, Houston. On March 26, 2018, the Board of Regents of the University of Oklahoma formally announced that Gallogly would be serving in the capacity of OU's presidency following the retirement of David L. Boren. The selection process in which he was chosen as Boren's successor came under fire for its secrecy. After less than a year as president, Gallogly announced his retirement on May 12, 2019.
On behalf of the Gallogly Family Foundation, James and Janet Gallogly pledged to donate $1M to the University of Colorado, supporting creation of the Gallogly Events Center. The center is named in honor of father Tommy M. Gallogly, a non-traditional adult student who earned bachelor's and master's degrees in education at UCCS. Formally dedicated in 2010, the building has been awarded Leadership in Energy and Environmental Design Gold certification.