Jessica Alba's 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 Guevara, on the FOX sci-fi television series Dark Angel. Co-created by Cameron, the series starred Alba, and ran for two seasons until 2002, earning her critical acclaim as well as a Golden-Globe nomination. Alba later revealed that she had suffered from an eating disorder while in preparation for Dark Angel.

Alba's most notable film roles have included 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, of which movie critic Mick LaSalle said that her performance while talking for long periods of time was on "shaky ground".

She then appeared in its sequel, in Into the Blue later that year, and Good Luck Chuck a few years later.] Alba went on to host the 2006 MTV Movie Awards and performed sketches spoofing the movies King Kong, Mission Impossible 3, and The Da Vinci Code.

In 2008, Alba appeared in her first horror-film role in The Eye, a remake of the Hong Kong original. In February, she hosted the Academy of Motion Picture Arts and Sciences's Science and Technical Awards. Later in the year, she starred in The Love Guru. She has signed on to star in An Invisible Sign of My Own to be released in 2009.

Alba has been represented by talent agent Patrick Whitesell.
In 2006, readers of Askmen.com voted Alba No. 1 on 99 Most Desirable Women, while in 2007, Maxim Magazine placed Alba on the number 2 spot of their "Top 100", after Lindsay Lohan. Both GQ and In Style had Alba on their June covers, and in May, after eight million votes, FHM (UK and USA editions) named Alba the winner as "2007’s Sexiest Woman in the World". Alba continues to be regarded as one of the world's most attractive women, being named to Maxim's Hot 100 in 2008.

Alba has been well-received in popular culture. She received the Teen Choice Award for Choice Actress and Saturn Award for Best Actress (TV) for her role in Dark Angel. She has frequently appeared on Maxim's Hot 100 list. In 2006, Alba received an MTV Movie Award for "Sexiest Performance" for Sin City.

Her acting has also drawn criticism, however, as she was nominated for a 2007 Razzie Award for Worst Actress for her performances in Awake, Good Luck Chuck, and Fantastic Four: Rise of the Silver Surfer. She was also nominated for the same award in 2005 for her performances in Fantastic Four and Into the Blue.