Berlanti was born in Rye, New York. His parents are Barbara Moller Berlanti and Eugene Berlanti. Greg has one sister, Dina and is the uncle of two nieces. He described his early life in an August 2004 interview with Entertainment Weekly: "We were Italians in a town of WASPs" and his family was not "doing as well as 90% of the community."After each of his shows is his Berlanti Television logo which features a family with their backs to the audience and a quote which says "Greg move your head!" which is actually what his father Gene used to yell at him when he was blocking the television screen.

Berlanti is openly gay.

Berlanti studied writing at Northwestern University and participated in many activities including Delta Tau Delta fraternity. He was a writer and producer on Dawson's Creek and its short-lived spin-off Young Americans. He is best known as being the creator, executive producer, and showrunner of Everwood. He also co-created the short-lived series Jack & Bobby.

Berlanti also wrote and directed the film Broken Hearts Club, about young gay friends in West Hollywood which he based on his own circle of friends at the time.

In August 2006, Berlanti announced a new deal with Touchstone Television and ABC to create new pilots. In conjunction with the announcement, Berlanti announced a parting of the ways with longtime creative partner Mickey Liddell. At the same time, news surfaced that Berlanti was acting as a consultant for the new ABC series Brothers & Sisters. The previous executive producer, Marti Noxon, had left the show after conflict with creator Jon Robin Baitz. Berlanti now serves as an executive producer for the series.

Berlanti was also the executive producer of Dirty Sexy Money which debuted on ABC on September 26, 2007.

With Marc Guggenheim, Berlanti is the co-writer of Eli Stone, a television pilot for ABC which debuted as a mid-season replacement in 2008. Berlanti also serves as executive producer. Berlanti was instrumental in the pilot's promotion of the theory that a mercury-based vaccine preservative causes autism. This theory is not supported by scientific evidence, but has contributed to decreased vaccination rates that endanger children. Berlanti expressed no qualms about the pilot and defended it before it aired.

Berlanti co-wrote and was briefly attached to direct the 2011 Green Lantern film. He has also directed the film Life As We Know It starring Katherine Heigl and Josh Duhamel.

Writer

• The Broken Hearts Club: A Romantic Comedy (2000)
• "Jack & Bobby" (2004)
• "Everwood" (2002-2006)
• "Eli Stone" (2007)
• "Brothers & Sisters" (2006-2007)

Producer

• "Everwood" (2002-2006)
• "Brothers & Sisters" (2006-2007)
• "Dirty Sexy Money" (2007)

Director

• The Broken Hearts Club: A Romantic Comedy (2000)
• Life As We Know It (2010)