Harmon began acting in 1995 after being discovered on a plane by David Hasselhoff. She then starred in several television series, including Baywatch Nights, Baywatch and C-16: FBI; she also appeared in the 1998 film, Lawn Dogs, which received only a limited theatrical release. In the early 2000s, Harmon became better known as playing Abbie Carmichael on the series Law & Order, a role she played from 1998 to 2001. During this time, she also voiced Barbara Gordon in the animated film, Batman Beyond: Return of the Joker, replacing Stockard Channing, as well as appearing on Law & Order.

Harmon left Law & Order to concentrate on her film career, saying that she preferred working in film than television. After appearing in the 2001 direct-to-video film Good Advice, she had a major role in Agent Cody Banks, playing the CIA handler of a teenage agent (Frankie Muniz). The film opened in March 2003 and became a minor hit, grossing $47 million. Although Harmon was originally scheduled to appear in the sequel, the producers chose to take a more comedic approach, and replaced Harmon with Anthony Anderson. In 2006, Harmon co-starred with Cuba Gooding Jr. and James Woods in the direct-to-DVD political suspense drama End Game.

In 2006, Harmon starred as the lead in the ABC pilot Secrets of a Small Town. Despite testing highly with focus groups, the pilot was not picked up by ABC due to its high budget. She also starred in another failed television show on NBC, Inconceivable. The program was canceled after two episodes. In 2007, she starred in another ABC pilot, Women's Murder Club. The police drama was picked up, but cancelled after the first season with only 13 episodes produced and aired. In April 2008 Angie Harmon Goes Naked for Allure Magazine is among five actresses who strip down to their birthday suits for the May issue of Allure magazine. She appears nude along with Gabrielle Union; Zoe McLellan (of ABC's "Dirty Sexy Money"); singer and actress Jill Scott; and "Ugly Betty" co-star Ana Ortiz.

• Living Proof (2008) (TV) .... Lilly Tartikoff
• "Women's Murder Club" .... Lindsay Boxer (13 episodes, 2007-2008)
  ... aka wmc (USA: short title)
       - Never Tell (2008) TV episode .... Lindsay Boxer
       - And the Truth Will (Sometimes) Set You Free (2008) TV episode .... Lindsay Boxer
       - Father's Day (2008) TV episode .... Lindsay Boxer
       - FBI Guy (2008) TV episode .... Lindsay Boxer
       - To Drag & to Hold (2007) TV episode .... Lindsay Boxer
        (8 more)
• Glass House: The Good Mother (2006) (V) .... Eve Goode
  ... aka Glass House: The Good Mother (Australia: DVD title)
  ... aka The Glass House 2 (Europe: English title)
• Seraphim Falls (2006) .... Rose
• End Game (2006) .... Kate Crawford
• "Secrets of a Small Town" .... Bethany Steele (1 episode, 2006)
       - Pilot (2006) TV episode .... Bethany Steele
• Fun with Dick and Jane (2005) .... Veronica Cleeman
  ... aka Alternative Career (Philippines: English title)
  ... aka Fun with Dick & Jane (USA: poster title)
• "Inconceivable" (2005) TV series .... Dr. Nora Campbell (unknown episodes)
• The Deal (2005) .... Anna
• Agent Cody Banks (2003) .... Ronica Miles
  ... aka Agent Cody Banks, L' (Canada: French title)
• Video Voyeur: The Susan Wilson Story (2002) (TV) .... Susan Wilson
• Good Advice (2001) .... Page Hensen
• "Law & Order" .... A.D.A. Abbie Carmichael (72 episodes, 1998-2001)
  ... aka Law & Order Prime (USA: informal title)
       - Deep Vote (2001) TV episode .... A.D.A. Abbie Carmichael
       - Judge Dread (2001) TV episode .... A.D.A. Abbie Carmichael
       - School Daze (2001) TV episode .... A.D.A. Abbie Carmichael
       - Brother's Keeper (2001) TV episode .... A.D.A. Abbie Carmichael
       - All My Children (2001) TV episode .... A.D.A. Abbie Carmichael
        (67 more)
• Batman Beyond: Return of the Joker (2000) (V) (voice) .... Commissioner Barbara Gordon
  ... aka Batman of the Future: Return of the Joker (Europe: English title: cut version)
  ... aka Batman of the Future: Return on the Joker (UK: TV title)
  ... aka Return of the Joker (USA: informal English title)
• "Batman Beyond" .... Commissioner Barbara Gordon (1 episode, 2000)
  ... aka Batman of the Future (Europe: English title) (UK)
       - King's Ransom (2000) TV episode (voice) .... Commissioner Barbara Gordon