Bynes began acting at 7 when she appeared in a TV advertisement for Brunch Crunch Candies. She also appeared in the stage plays Annie, The Music Man, and The Sound of Music, among others, when she was a child.
The former actress disclosed during an interview that she was discovered by Nickelodeon producers Brian Robbins and Dan Schneider when she attended a comedy camp at the Laugh Factory in Los Angeles, CA, USA.
Amanda was later cast in the Nickelodeon comedy All That and Figure It Out game show. She finally got her live-action sketch comedy show, The Amanda Show, in 1999. The show last aired in 2002.
The fashion designer has starred in several movies and TV series. According to her IMDb, some of her popular films and TV series include:
| Year | Movie/TV series | Role |
| 1998 | Sports Theater with Shaquille O'Neal | Caroline Hanley |
| 2001 | The Nightmare Room | Danielle Warner |
| 2002 | Big Fat Liar | Kaylee |
| 2003 | What a Girl Wants | Daphne Reynolds |
| 2005 | Lovewrecked | Jenny Taylor |
| 2006 | She's the Man | Viola |
| 2002–2006 | What I Like About You | Holla Tyler |
| 2007 | Hairspray | Penny Pingleton |
| 2008 | Living Proof | Jamie McGrath |
| 2009 | Canned | Sarabeth |
| 2010 | Easy A | Marianne |
Amanda is no longer into acting. She retired in June 2010, with her last film project being Easy A. She tweeted in a now-deleted tweet:
Being an actress isn't as fun as it may seem. If I don't love something anymore I stop doing it. I don't love acting anymore so I've stopped doing it. I know 24 is a young age to retire but you heard it here first. "I've #retired.
In August 2007, Amanda launched her accessory and clothing line, Dear by Amanda Bynes. In 2022, she released her single Diamonds, featuring her fiance, Paul Michael.
