Born in Schwenningen, Germany, Seidenberg was selected by the Philadelphia Flyers in the sixth round (172nd overall) of the 2001 NHL Entry Draft. The defenseman played a total of 859 career regular season games with six teams, including the New York Islanders in his final two years in the NHL.

He began his NHL career playing with the Flyers, totaling 20 points in 92 games over the course of three seasons (2002-03 through 2005-06). He played the next year and a half (2005-06 through 2006-07) with the Phoenix Coyotes (now Arizona), scoring 13 points (two goals and 11 assists) in 66 games. He was traded to the Carolina Hurricanes during the 2006-07 season and played three seasons there, scoring 51 points (six goals and 45 assists) in 137 games. Seidenberg signed with the Florida Panthers at the start of the 2009-10 season, scoring 23 points (two goals and 21 assists) in 62 games, before he was traded to the Boston Bruins. He would spend seven years (2009-10 through 2015-16) with the Bruins. Seidenberg had a career year during the 2010-11 regular season, scoring seven goals and 25 assists for 32 points. That same season, he would score a goal and ten assists (11 points) in 25 NHL playoff games, helping the Bruins win the Stanley Cup.

Seidenberg finished his career with the Islanders, playing in 101 games during the 2016-17 and 2017-18 seasons, scoring 27 points (five goals and 22 assists).

Internationally, Seidenberg has represented Germany at three Olympic Games and was a member of Team Europe at the 2016 World Cup of Hockey.

Seidenberg continues to reside on Long Island with his wife and three children. He will continue to work with the Islanders organization as a member of the Player Development staff.

Dennis Seidenberg Statement

"After fifteen years of living my dream of playing in the NHL, I have decided it is time for me to retire from the game I love. It hasn't been an easy decision, but I know it is the right one.

I want to take this opportunity to thank my coaches, teammates and the organizations I played with over the years. I have been lucky enough to represent my native Germany in three Olympic Games, an indescribable honor. There was no greater thrill than lifting the Stanley Cup with the Boston Bruins in 2011.

That group of guys will always hold a special place in my heart.

I want to thank the greatest fans of the best game in the world. I have never taken for granted what a privilege it is to play this game, and how the important the fans are. I will cherish the experiences and memories I have for the rest of my life.

Finally, I want to thank my family for all their support in letting me live out my dreams.

Thank you."