Portman's parents met at a Jewish student center at Ohio State University, where Portman's mother was selling tickets. Portman's father returned to Israel, but the two corresponded and were married when Portman's mother visited Israel a few years later. When Portman was three years old, her family moved from Israel to her mother's native United States, where her father pursued his medical training. The family lived in Washington, D.C. in 1984 and then Connecticut in 1988, before finally settling down in Syosset, New York in 1990. Portman has said that although she "really love the States", her "heart's in Jerusalem. That's where I feel at home."

Portman is an only child and very close to her parents, who are often seen with her at movie premieres; her mother always accompanied pre-adult Portman to movie shoot locations.

Early career Portman started taking dancing lessons at the age of four, performed in local troupes, and dreamed of dancing on Broadway. At the age of ten Portman was discovered in a pizza parlor by an agent for Revlon, who offered her an opportunity to model. She asked to be introduced to acting talent scouts, and took "Portman", her grandmother's maiden name, as her professional stage surname.

Starting at age 13, Portman spent her school holidays attending upscale theatre camps Stagedoor Manor and Usdan Camp, where she forged her love for acting, playing roles in the camp productions such as the title character in Anne of Green Gables, Dream Laurey in Oklahoma! and Hermia in A Midsummer Night's Dream. In 1993 Portman was handed her first professional role as an understudy for the off-Broadway musical Ruthless!.

Her inaugural experience in professional theatre led her to audition for Luc Besson's 1994 film Léon (aka The Professional). She was initially turned down for the role due to her youth, but further auditioning won her the part. Soon after Portman was given the part, she took Portman as her stage name in the interest of privacy. In the film, Portman plays an orphaned girl who befriends a much older assassin. Léon opened on November 18, 1994 and marked her feature film debut at age thirteen. That same year appeared in the short film Developing which aired on television.

1995-1999 She was cast in the high-budget action film Heat. Although she had a small role, she starred alongside some of the industry's biggest names such as Robert De Niro, Al Pacino and Val Kilmer. Following the success of Leon, Portman had gained considerable fame for her performance and was approached for the role of Marty in Ted Demme's Beautiful Girls. Following an audition, she was cast in Woody Allen's comedy-musical Everyone Says I Love You. She was also given a role in Tim Burton's famously star-studded Mars Attacks!. She was the first choice to play Juliet in the 1996 film Romeo Juliet, but turned it down because of the adult content and the age difference between her and Leonardo DiCaprio.

In 1996, to Portman's surprise, casting director for the new Star Wars films Robin Gurland contacted her to see if she was interested in playing the female lead in the new films. Portman, still only 14 years old and having never seen the original three Star Wars films, was speculative at first about the commitment she was making and what impact it would have on her life, as the role would ultimately see her participate in three films over the course of a decade. After meeting with George Lucas and producer Rick McCallum she signed on to the prequel trilogy. Portman then auditioned for the role of Anne Frank in the Broadway revival of The Diary of Anne Frank. The decision to participate in this production caused her to pull out of the film The Horse Whisperer. In mid-1997, production began on the first of the three Star Wars prequel films, Star Wars: Episode I The Phantom Menace.

She returned to complete her junior year in high school, whilst studying she also performed The Diary of Anne Frank. She did eight shows a week while attending classes full-time. The play was performed for a month at the Colonial Theater in Boston before making its Broadway debut at the Music Box Theater in early December. She would receive a Tony nomination for her role as Anne Frank. She was also offered a role in the film Anywhere But Here, but after reading the script turned down the role as her character was involved in a sex scene. Director Wayne Wang and actress Susan Sarandon rushed to her support and demanded a rewrite of the script, allegedly saying they would not continue their involvement in the film unless the young actress's wishes were respected. Portman was shown a new script and she happily joined the project. In early 1999, The Phantom Menace opened and became the highest grossing film of the year and the highest grossing film out of the Star Wars series. Its massive audience and mainstream appeal saw Portman become an instant star. Portman then signed on to play a persevering teenaged mother in Where the Heart Is. Anywhere But Here opened in late 1999; she received a Golden Globe nomination for Best Supporting Actress for her role as Ann August.

2000-2005 After filming Where the Heart Is, Portman moved into the dorms of Harvard to pursue her bachelor's degree in psychology. She graduated in 2003. In July 2001, Portman opened in New York's Public Theatre production of Chekhov's The Seagull, directed by Mike Nichols, playing the role of Nina alongside co-stars Meryl Streep, Kevin Kline and Philip Seymour Hoffman. The play opened at the Delacorte Theatre in Central Park. That same year she was one of many celebrities who made cameo appearances in the comedy Zoolander. Attack of the Clones was filmed in Sydney during this time, including additional production in London.

In 2002, Attack of the Clones opened around the world. That same year, Portman was featured in top attractiveness lists in several publications (Sexiest Female Movie Star, Australian Empire Magazine ; 25 Hottest Stars Under 25, Teen People; 50 Most Beautiful People, People). Portman was cast in a small role in the film Cold Mountain alongside Jude Law and Nicole Kidman.

In 2004, Portman had starring roles in the independent movies Garden State and Closer. Garden State was an official selection of the Sundance Film Festival and won Best First Feature at the Independent Spirit Awards. Her role of Alice in Closer saw Portman win a Supporting Actress Golden Globe as well as a Best Supporting Actress Oscar nomination.