We are Grant Thornton

Chicago, Illinois

  • Healthcare
  • Technology, media & telecommunications
  • Retail & consumer brands
Service Experience
  • Advisory

Mark Sullivan




Executive summary

Mark is an experienced, optimistic, achievement-driven executive and board director for large private companies ($3-7B) and not-for-profit organizations. As an accomplished Senior Partner entrusted with overseeing a substantial operation at Grant Thornton LLP (GT), Mark has gained invaluable experience that mirrors the responsibilities of a CEO. Leading large teams and managing diverse portfolios, he has successfully navigated the intricacies of running a complex business within the firm.


Mark is lauded as a transformational and collaborative leader, developing effective strategies and leading the execution of successful initiatives. His investigative background has proven to be a unique skill in the boardroom, allowing him to delve into complex and technical issues from a governance perspective — then present these issues in a manner that is understood by all.




Professional qualifications and memberships

  • Center for Interviewing Standards and Assessment, Advisory Committee Member
  • National Immigrant Justice Center, Leadership Board Member
  • American Society for Industrial Security
  • Certified Fraud Examiner (CFE)
  • Certified Forensic Interviewer (CFI)
  • Certified Protection Professional (CPP)



Community involvement

  • Choose DuPage, Board Member
  • Union League Club of Chicago
  • World Business Chicago, Board Member




  • BS, Administration of Justice, Southern Illinois University


Search for people at Grant Thornton


Enter a name and/or keywords such as service area, industry or location to get to know our business leaders — partner, principal or managing director. We look forward to hearing from you.