• University of San Diego, B.A. in English, 1999
  • University of Iowa College of Law, J.D., 2005


  • Illinois
  • Federal Bar, Northern District of Illinois
  • Federal Trial Bar, Northern District of Illinois


  • Illinois State Bar Association
  • Chicago Bar Association

Sean O'Callaghan

Sean O’Callaghan is a partner at O’Mara Gleason O’Callaghan, where his practice focuses on general business counseling and litigation. Sean is also presently working toward his LLM in Financial Services at Chicago-Kent College of Law, the focus of which has been on market regulation, enforcement and litigation of securities and commodities law matters, mergers and acquisitions, and arbitrations.

For the first eight years of his legal career Sean served the people of Illinois as an Assistant State’s Attorney in the Cook County State’s Attorney’s office, where he tried numerous cases to juries and argued hundreds of motions and bench trials.

After starting his career in the Appellate Division, he moved up through the trial ranks prosecuting every type of criminal case from DUI to murder.

Sean attended the University of Iowa, College of Law, where he graduated with distinction. While in law school, he was a member of the Iowa Law Review, a Van Oosterhout Moot Court competitor, and a member of the Moot Court Board. He also clerked in the real estate practice group of Wildman Harrold (now Locke Lord) in Chicago.

He earned his bachelor’s degree from the University of San Diego, where he was a four-year recipient of the university’s Dean’s Scholarship and graduated with departmental honors in English. Between college and law school, he worked in commercial real estate leasing in San Diego.

Sean’s father is a proud Chicago Police Officer, now retired, and his mother recently retired from a career as a professor at a local university.

Sean lives in Chicago with his wife and two children.

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