Alba was born in Pomona, California to Mark Alba and Cathy Jensen. Her father is a Mexican American, while her maternal grandfather was of Danish descent and her Canadian maternal grandmother was of French, English and Italian descent. Alba was raised in an Air Force family, her brother Joshua Alba and her grandparents until she was sixteen. She grew up a sports fanatic. Her father's Air Force career took the family to Biloxi, Mississippi, and Del Rio, Texas, before they settled back in California when she was nine. Alba's early life was marked by a multitude of physical maladies; she suffered collapsed lungs twice, had pneumonia 4-5 times a year, a burst appendix, a cyst on her tonsils and asthma. This served to isolate her from other children at school because, as she claims, she was in the hospital so often that no one knew her well enough to befriend her. She also revealed on The Tonight Show with Jay Leno that she suffered from obsessive-compulsive disorder as a child. Her health improved, however, when her family moved to California, though occasionally she still exhibits some symptoms of OCD [citation needed].

Alba had expressed interest in acting since the age of five. She took her first acting class at age twelve, and she was signed by an acting agent nine months later.

Alba's first appearance in film was a small role in the 1994 feature Camp Nowhere as Gail. She was originally hired for two weeks but her role soon turned into a two month job when the actress in one of the more prominent roles in the film dropped out; Alba was picked to replace her because her hair matched that of the original actress [citation needed].

Young Alba appeared in two national TV commercials for Nintendo and J.C. Penney; she was later featured in several independent films. She branched out into TV in 1994 with a recurring role as the insufferable young snob, Jessica, in three episodes of the Nickelodeon comedy series The Secret World of Alex Mack. She then performed the role of Maya in the first two seasons of the TV series Flipper. Under the tutelage of her lifeguard mother, Alba learned to swim before she could walk, and she was a PADI-certified scuba diver, skills which were put to good use on the show, which was filmed in Australia. In 1995, she appeared in the film Venus Rising as Young Eve.

After graduating from high school at the age of 16, Alba studied acting with William H. Macy and his wife, Felicity Huffman, at the Atlantic Theater Company, which was developed by Macy and Pulitzer Prize-winning playwright and film director, David Mamet.

In 1998, she appeared as Melissa Hauer in a first-season episode of the Steven Bochco crime-drama Brooklyn South, as Leanne in two episodes of Beverly Hills 90210 and as Layla in an episode of The Love Boat: The Next Wave. In 1999, she appeared in the Randy Quaid comedy feature P.U.N.K.S..

Alba rose to greater prominence in Hollywood in 1999 after appearing as a member of a snobby high school clique in the Drew Barrymore romantic comedy Never Been Kissed, and as the female lead in the 1999 comedy-horror film Idle Hands, opposite Devon Sawa. But her big break came when writer/director James Cameron picked Alba from a pool of 1,200 candidates for the role of the genetically-engineered super-soldier, Max Guevera on the Fox sci-fi TV series Dark Angel. Co-created by Cameron, Alba was the definitive star in the series which ran for two seasons before being canceled in 2002. Since then her most notable roles have been as an aspiring dancer/choreographer in Honey, exotic dancer Nancy Callahan in Sin City and as the classic Marvel Comics character Sue Storm, the Invisible Woman in the Fantastic Four. Jessica then went on to hosting the 2006 MTV Movie Awards and did sketches spoofing King Kong, Mission Impossible 3, and The Da Vinci Code.

She once told Dark Angel producer, James Cameron, that she did not want to direct because it appeared to be too difficult an undertaking, but he responded with the prediction that she would end up directing sooner than she expected [citation needed].

Apparently, Alba fears being typecast as a sex kitten.[1] However, she admits, "Somehow, I don't think this is happening to Natalie Portman." In the interview, Alba says she wants to be taken seriously as an actress but believes she needs to do movies that she would otherwise not be interested in to build her career, stating that eventually she hopes to be more selective in her film projects [citation needed].

Alba suffered anorexia[2] and a kidney infection in 2001. She also now suffers from motion sickness, which developed after childhood.

Alba was engaged to her Dark Angel co-star Michael Weatherly, but it was called off. In January 2005, she began dating Cash Warren, a director's assistant on Fantastic Four, whom she met when filming that movie.

Regarding children, Alba has stated:

    "I'm really girly when it comes to kids. I've been surrounded by kids my whole life because I'm the oldest of 15 cousins — I've been changing diapers since I was six. I want to have a couple, for sure". [citation needed]

Alba announced on the UK teen website "Teen Today" in 2005, prior to the birth of her brother's child, that she was beginning a children's clothing line:

    "About four of my girlfriends have babies so they have no time for me. I figure if I can do baby clothes maybe they'll have more time to hang out!"[3]

She is a self-professed animal lover (although she dislikes reptiles and rodents). She also revealed that she "hates cats" in an interview with Conan O'Brien in 2001 [citation needed].

She is an enviromentalist, and owns a Lexus hybrid. She has also bought her parents a Toyota Prius [citation needed].

During an interview with GQ magazine, Alba said that in her teen years she became a born-again Christian in a rebellion against her parents but told Access Hollywood that she abandoned this because "a lot of people gave me a lot of grief for just being a woman and made me feel ashamed for having a body because it 'tempted men'".[4]

As the daughter of conservative parents, Alba, whose grandparents did not even allow her to wear a bathing suit around the house, maintains a no-nudity clause in her contract, though she has claimed she had been willing to be nude in Sin City. She remarked of a GQ shoot in which she was scantily-clad:

    "They didn't want me to wear the granny panties, but I said, 'If I'm gonna be topless I need to wear granny panties"