Mr. Riordan graduated Summa Cum Laude from Molloy College in 2000 and received his law degree from St. John's University School of Law in 2004, where he was a member of the Journal of Legal Commentary. Upon admission to the practice of law, Mr. Riordan began representing claimants before the Social Security Administrations Office of Disability Adjudication & Review and the various New York State/City Retirement Boards. He has also represented many people in Article 78 Appeals before the Supreme Court of New York as well as the Appellate Division 3rd Department. He has lectured to many unions, including Correction Officers, Police Officers, Detectives, Teachers and Laborers, regarding their disability rights.

Sean is an outspoken advocate for First Responders, having joined with advocacy groups and Congressional leaders to help pass legislation that affords greater health care and benefits to men and women that respond to emergency situations. He has been interviewed by Court TV and Eyewitness News, as well as various other media outlets, regarding his work in this area.  Mr. Riordan is also very involved in the Irish-American community. As President of the Nassau County Brehon Law Society and member of The Society of the Friendly Sons of St. Patrick of Long Island, Sean has been an advocate for human and civil rights in Northern Ireland and a proponent of the continued peace process. In 2008 Mr. Riordan was named one of the Top 100 Irish-American attorneys in the United States by Irish America Magazine and the Irish Voice.  

Sean is also adjunct professor at Molloy College, teaching The Philosophy of Law and Political Philosophy. He is also a member of the Association of Trial Lawyers of America; American Bar Association; New York State Bar Association and the New York County Lawyers Association. Mr. Riordan sits on the board of directors for the Irish Cultural Centre of Long Island and Great Hunger Memorial. He lives in Suffolk County with his wife and two children.