He retired from Wall Street in 2016 and is started a company called The Athletes Village which is building a platform to motivate and enhance the sports experience for youth athletes, their parents and coaches by connecting them through a Q&A/Search platform with elite athletes and experts in all the fields of sports (coaching, parenting, nutrition, psychology, strength training, injury prevention, etc.)  Henderson was married to Summer Sanders from 1997 to 2001. In 2006, Mark married Tamara Blanchard. They have two children: Brooke & Brady, a Bernese Mountain Dog (Harry) and a Double Dapple Dachshund (Gator). Mark and his family live in Bend, Oregon. Since his retirement from competitive swimming, Henderson has been a member of USA Swimming's Athlete Executive Council (AEC) (2000–2008), USA Swimming Board member (2000–2008), United States Olympic Committee Athlete Advisory Council (AAC) member (2000–2008), Chair of the AAC (2004–2008), current Board member of the Leo Brien Foundation, Olympic solidarity representative to Zimbabwe (2000–present), Co-founder of S.W.I.M (Swim With Inspiration and Motivation) learn-to-swim program for inner-city youth in San Francisco, and he is also a participant/ member in the Big Brother Program (1988–present) and Swim Across America. In 2008, Henderson was the recipient of the USA Swimming Athlete Appreciation Award. Mark has also been very active giving back to the global swimming community by answering questions from athletes, parents and coaches located all over the world on the platform The Athletes Village