Seaver was a key player on the 1969 "Mircale Mets" World Series team.
Hall of Fame pitcher Tom Seaver has been diagnosed with dementia, the Seaver family announced in a statement from the Baseball Hall of Fame.
"Tom will continue to work in his beloved vineyard at his California home, but has chosen to completely retire from public life," the Seaver family said. "The family is deeply appreciative of those who have supported Tom throughout his career, on and off the field, and who do so now by honoring his request for privacy. We join Tom in sending warmest regards to everyone."
Former New York Mets teammate Art Shamsky detailed Seaver's health issues in his book, After the Miracle. Shamsky, 77, wrote that Seaver was suffering from short-term memory loss.
Seaver pitched from 1967 to 1986 for four teams, but is noted primarily for his time with the Mets, especially for his role in the team's 1969 World Series win. During his 20-year career, Seaver recorded 311 wins, 3,640 strikeouts, 61 shutouts and a 2.86 ERA.
He won the National League Rookie of the Year Award in 1967 and received three NL Cy Young Awards as the league's best pitcher.
The Mets released a statement on Thursday saying they plan to recognize Seaver this season at the anniversary of the 1969 World Series.
"Although he's unable to attend the '69 Anniversary, we are planning to honor him in special ways and have included his family in our plans," the team said. "Our thoughts are with Tom, Nancy and the entire Seaver family."
Seaver, 74, was inducted into the Hall of Fame in 1992 with one of the highest percentage of votes (98.84%).