Jennifer Grant was born on February 26, 1966, in Burbank, California. Her parents divorced when she was only two years old. The reasons given for their divorce were that her father was unable to find his "perfect wife"; in addition, there was a 33-year age difference. Jennifer had a close relationship with her father for the rest of his life. Partly because her father did not want her to become an Actress, she tried other things for several years. As a teenager during high school at Brentwood School in Los Angeles and on break from college she worked as a babysitter, stock clerk at the Village store in Pacific Palisades, grocery store checkout cashier at the Rainbow Grocery in Malibu, and waitress at the Pioneer Boulangerie restaurant in Santa Monica. After graduating from Stanford University in 1987 with a degree in American Studies, she worked for a law firm, and followed that with a job as a chef at Wolfgang Puck's Spago restaurant in Beverly Hills. When her father died in 1986, he left her half his estate, worth several million dollars; the other half of the estate went to her stepmother Barbara Harris Grant, with whom Jennifer has a close relationship.

In 1993, seven years after her father's death, Grant played her first acting role in the Aaron Spelling television drama Beverly Hills, 90210, in the recurring role of Celeste Lundy. She appeared as a guest star in a variety of shows including Friends, and later appeared in several movies. In 1999, she was the lead Actress in the WB television sitcom Movie Stars.

Grant was married to Randy Zisk for three years, but the marriage ended in divorce in 1996.

Grant gave birth to a son, Cary Benjamin, on August 12, 2008.

Her memoir, Good Stuff: A Reminiscence of My Father, Cary Grant (2011), is a portrait of her relationship with her father, who was 62 when she was born and who died 20 years later. The title refers to a favorite expression of his, said in reference to things he approved of or situations he was happy about.