The six-time Pro Bowler revealed his plans at Saturday's Health & Fitness Expo at MetLife Stadium.
"I just decided that last week. Two more years, get my Super Bowl, have a little bit more fun, and then I'm going to go change the world in the mental health space," the 33-year-old Marshall told Newsday.
Marshall's plan to bring awareness to mental health is one that hits close to home. He was diagnosed with borderline personality disorder in 2011.
Marshall, who signed a two-year, $12 million deal with the Giants after being released from the Jets, has eight 1,000-yard seasons since being drafted in 2006.
Marshall has career totals of 941 receptions, 12,061 receiving yards and 82 touchdown catches in his 11 seasons.