Sean P. Sullivan

Sean P. Sullivan is a leading family law attorney with a practice focused on complex domestic relations matters, mediation, and related business and inheritance disputes. Known for his thoughtful advocacy and practical approach, Sean guides clients through highly contested and emotionally difficult matters with a combination of courtroom skill, strategic negotiation, and direct communication.

Sean represents clients in all areas of family law, including contested and uncontested divorce, maintenance, child support, post-decree matters, and prenuptial agreements. Drawing on his background in business formation, valuation, and litigation, he is particularly experienced in divorce matters involving closely held businesses, executive compensation packages, and other complex financial issues. He also handles inheritance-related litigation, including will contests and fiduciary disputes.

While Sean is recognized as a strong courtroom advocate, he also places significant emphasis on achieving practical and efficient resolutions outside of litigation whenever possible. As a trained mediator, he assists couples and co-parents in resolving sensitive family matters privately and constructively. His mediation credentials were earned through the mediation certification program at Northwestern University, where he trained under nationally respected professionals in the field.

Sean was admitted as a Fellow of the American Academy of Matrimonial Lawyers in August 2025 and currently serves on the board of the Illinois Chapter of the AAML. He is also Chair of the DuPage County Bar Association Family Law Section for 2026 and a past chair of the association’s Professional Responsibility Section. In addition, Sean serves on the Board of Directors for DuPage County Court Appointed Special Advocates (CASA), frequently acts as a court-appointed guardian ad litem and mediator within the DuPage County court system, and is active in the Illinois State Bar Association Child Law Section Council. He also participates in the GAL Best Practices Subcommittee, assisting the Illinois Supreme Court with standardized procedures and forms.

Sean earned his J.D., along with a Certificate in Litigation, from Western Michigan University Cooley Law School in 2009. He also holds a Bachelor of Arts degree in Psychology and Political Science from the University of Iowa, a background he often draws upon in negotiations and case strategy.

Sean was named a Super Lawyers attorney in Family Law in 2024, 2025 and 2026, an honor awarded to a small percentage of attorneys statewide for professional achievement and peer recognition.