Gallin was born in 1940 in New York, the son of middle class Jewish parents. He started in the mailroom of General Artists Corporation, eventually becoming a senior vice president and board member. During this time he played a role in booking The Beatles on The Ed Sullivan Show.
In 1969 he left GAC to pursue personal management and production. Since then he has managed the careers of Cher, Dolly Parton, Michael Jackson, Neil Diamond, Barbra Streisand, Mariah Carey, and Whoopi Goldberg.
He's produced over 20 movies as well as Broadway plays, and has been the CEO of Mirage Entertainment and Sports. He is a close associate of Steve Wynn, Barry Diller, David Geffen, Diane Von Furstenberg, and Calvin Klein.
His 70th birthday party was thrown at Donna Karan's West Village studio, attended by Patti LaBelle, Barbra Streisand, Joan Rivers, Bette Midler, Vera Wang, Renée Zellweger, Richard Gere, Sandra Bernhard, Les Moonves, and Ron Perelman.
In 1988 Gallin battled cancer.
In 1997, Gallin was sued by two former employees alleging sexual harassment. The lawsuit alleged Gallin asked them to coordinate sexual visits with young men, as well as to offer their sexual services to potential clients to secure relationships.
Gallin is openly gay.
Gallin married considerably younger artist and actor Bryan Fox on 11th February 2011.
- "Winner Takes All: Steve Wynn, Kirk Kerkorian, Gary Loveman, and the Race to Own Las Vegas", Christina Binkley. Hyperion, 2008. ISBN 1-4013-0236-X, 9781401302368. p. 133-134
- "The Mailroom: Hollywood History from the Bottom Up", David Rensin. Random House Digital, 2004. ISBN 0-345-44235-0, ISBN 978-0-345-44235-2. p. 77
- "Michael Jackson: the king of pop", Lisa D. Campbell. Branden Books, 1993. ISBN 0-8283-1957-X, 9780828319577. p. 288
- "Saint James Press gay and lesbian almanac", Neil Schlager. St. James Press, 1998. ISBN 1-55862-358-2, ISBN 978-1-55862-358-3. p. 245
- "The Barry Diller Story: The Life and Times of America's Greatest Entertainment Mogul", George Mair. John Wiley and Sons, 1998. ISBN 0-471-29948-0, ISBN 978-0-471-29948-6. p. 206
- "How to Lose Friends and Alienate People", Young, Toby. ISBN 1-4587-2344-5, ISBN 978-1-4587-2344-4. p. 194
- "New York Magazine Vol. 29, No. 30", New York Media, LLC. p. 81
- "Hugh Jackman knocks 'em dead at Sandy Gallin party", New York Post. May 28, 2010. Accessed March 4, 2011
- "The Advocate", November 25, 1997. ISSN 0001-8996. p. 34