Richman was hired by the New York Daily Mirror as a copy boy in 1942 and worked there until the newspaper folded in 1963. He wrote one of New York's most popular baseball columns, "The Armchair Manager."
He joined the Mets as director of promotions, then became publicity director and was named traveling secretary in 1980. He was replaced as traveling secretary in December 1988 after he criticized the postseason share he was awarded by players. This was not the first time he felt slighted by the players. In 1986, Darryl Strawberry, Dwight Gooden and Kevin Mitchell were the only players who voted in favor of giving him a full World Series share. "And that was the year I had to bail four players out of jail in Houston during the season," Richman said. "After they voted me a half-share, I told them they could keep their $43,000. And I told them not to call me the next time they wound up in jail." In 1994, he said then Mets co-owner Nelson Doubleday often made anti-Semitic remarks in front of him.
Richman was hired as the Yankees vice president of media relations in May 1989 and became a senior adviser in 1995. Richman stopped working following a heart attack in 2006.
In 1986, Richman was the traveling secretary for the Mets and was given the "Mookie Ball" by right field umpire Ed Montague the night of Game 6 the 1986 World Series. At an auction in 1992, actor Charlie Sheen payed $93,500 for the Ball which went through Bill Buckner's legs capping the miraculous Met comeback. Richman gave all the proceeds to charity.
Richman has been credited with recommending Joe Torre for the job of manager while with the Yankees in 1995. Upon learning of Richman's death in 2009, Torre said “He was a dear friend, and I will forever be grateful for having him whisper in George's ear about me managing the Yankees.”
Richman also aided other organizations. Richman came to Milwaukee in April 1970 and helped Bud Selig get the Milwaukee Brewers started after Selig purchased the Seattle Pilots in bankruptcy court and moved the franchise.
Richman's contacts in and out of baseball became legendary. He was the best man at Don Larsen's wedding. Willie Mays was his best man when Richman got married at 54 and the ushers were Ralph Kiner, Ernie Banks, Ralph Branca, Joe Torre, Dick Williams, Lee Mazzilli, Joe Pignatano, Ted Sizemore and Doug Flynn. George Brett named his second son Dylan Richman Brett after him.
In 1999, Richman was inducted into the National Jewish Sports Hall of Fame.