Alanna Ubach made her acting debut in the 1993 made-for-television drama film ‘Moment of Truth: Why My Daughter?’ directed by Chuck Bowman. That same year, she also joined the main cast of the American educational children's television program ‘Beakman's World.’ She played the role of ‘Josie’ and remained a part of the show until 1993. Right after her exit from ‘Beakman's World,’ she made her big-screen debut in the 1993 American comedy-drama film ‘Airborne,’ directed by Rob Bowman. The film received mixed to negative reviews from critics. That same year, she also appeared in the American musical comedy film ‘Sister Act 2: Back in the Habit’ directed by Bill Duke. Despite opening to negative reviews, the film managed to come out as a box office success. She next appeared in films like ‘Renaissance Man’ (1994), ‘The Brady Bunch Movie’ (1995), ‘Layin' Low’ (1996), ‘Love Is All There Is’ (1996), ‘Clockwatchers’ (1997), ‘The Sterling Chase’ (1999), and ‘Shriek If You Know What I Did Last Friday The 13th’ (2000).
In 2001, she starred as ‘Serena McGuire’ in the American comedy film ‘Legally Blonde,’ directed by Robert Luketic. The film received mixed to positive reviews from critics and was a massive box office success, grossing over $141.8 million on a budget of $18 million. In 2003, Ubach returned to play her role as ‘Serena McGuire’ in ‘Legally Blonde 2: Red, White & Blonde,’ the sequel to the 2001 ‘Legally Blonde.’ Even though the film saw negative reviews upon release, it did decent business at the box office. The following year, she joined the voice cast of the American animated television series ‘Brandy & Mr. Whiskers’ where she voiced the character ‘Lola Boa.’ In 2005, she appeared in the American sports comedy film ‘Herbie: Fully Loaded,’ directed by Angela Robinson. The film opened to mixed reviews and was a major box office success. That same year, she also starred in the American independent comedy-drama film ‘Waiting…’ which was also a financial success.
Ubach next starred in ‘Hard Scrambled’ (2006), ‘Jekyll’ (2007), ‘Batman: Gotham Knight’ (2008), ‘Still Waiting…’ (2009), ‘Bad Teacher’ (2011), ‘Rango’ (2011), ‘A Haunted House’ (2013), ‘To the Bone’ (2017), ‘Gloria Bell’ (2018), and ‘Bombshell’ (2019). In 2019, she joined the cast of the American teen drama television series ‘Euphoria.’ The series was renewed for a third season in February 2022. She was last seen voicing the character ‘Skull’ in the 2021 computer-animated fantasy streaming television miniseries ‘Maya and the Three.’