|Date of birth:||March 21, 1974|
|Place of birth:||Omaha, Nebraska|
|High school:||La Salle College (PA)|
|College:||William and Mary|
|Coaching stats at PFR|
McDermott is a 1993 graduate of La Salle College High School, where he was named All-Southeastern Pennsylvania at defensive back in 1992. He was also a national prep champion wrestler in both 1992 and 1993. He went on to earn a bachelor's degree in finance while at the College of William and Mary, where he was an all-conference safety (1997), and also receiving Academic all-conference honors in 1996 and 1997, and NSCA Strength and Conditioning All-America accolades. Sean played safety alongside future All-Pro NFL safety Darren Sharper.
McDermott originally joined the Philadelphia Eagles in 1998 as a scouting administrative coordinator, a position he held until being promoted to assistant to the head coach in 1999. He then became defensive quality control coach and later assistant defensive backs coach. In 2003 he replaced Steve Spagnuolo as defensive backs coach, as Spagnuolo was assigned linebackers coach. In 2004, McDermott saw both of his starting safeties (Brian Dawkins and Michael Lewis) earn Pro Bowl berths for the first time in team history. Under McDermott's watch, Dawkins went on to earn two more Pro Bowl berths following the 2005 and 2006 seasons.
In 2007, McDermott was assigned linebackers coach, after Spagnuolo had left to take the defensive coordinator job for the New York Giants. On January 28, 2008, Eagles head coach Andy Reid named McDermott secondary coach again.
On May 18, 2009, McDermott was named the interim defensive coordinator as a result of defensive coordinator Jim Johnson's medical leave of absence. On July 24, 2009, due to the continuing decline of Johnson, the Eagles announced McDermott would take over as full-time defensive coordinator. Johnson died on July 28, 2009. McDermott implemented a variety of blitzes in his defense, thanks in part to his mentor, former Eagles defensive coordinator Jim Johnson.
McDermott was fired as the defensive coordinator on January 15, 2011.
- La Canfora, Jason (January 15, 2011). "Eagles fire defensive coordinator McDermott". NFL.com. Retrieved 2011-01-15.