Reece was born in La Jolla, California and raised in Saint Thomas, U.S. Virgin Islands. She returned to the U.S. mainland for the eleventh grade, when she took up sports.
Her father, who was Afro-Trinidadian "a native of Trinidad and Tobago", was killed in a plane crash when Gabrielle was five.
On November 30, 1997, Gabrielle married the Hawaiian big-wave surfer Laird Hamilton. She filed for divorce in January 2001, but reconciled a year later. They have two children together: daughters Reece Viola Hamilton (born in October 2003) and Brody Jo Hamilton (born on January 1, 2008 in Hawaii). She and Hamilton also are raising Izabella, Hamilton's daughter from a previous marriage. The Hamilton-Reece family splits time residing in Hawaii and Malibu, California. In the latter, she is known as a member of the "Malibu Mob", a group of celebrity friends and neighbors that includes actor John Cusack, hockey player Chris Chelios, tennis player John McEnroe, and actor John McGinley.