Alyson was born in Washington, DC in 1974. Her parents divorced in 1976 when she was only 2, and by 1978 (at the tender age of 4) she was living in Atlanta and working in commercials for Oreos, McDonalds, and Six Flags Amusement Parks.

In 1985 she moved from Atlanta to Los Angeles and began to pursue her acting career in earnest. She was casted in many movies but none of them gained her fame, until she audioned for "Buffy the Vampire Slayer." Although the part for Willow had already been casted, everyone was so impressed by Alyson's audition, that they gave her the part. She worked on the series for seven seasons.

Her work on the big screen includes such hits as My Stepmother is an Alien (1988) and the successful American Pie trilogy (1999-2003). She is proud of the success that the "American Pie" movies have found, and she is now widely known for being the "Band Camp Girl."

She and Buffy co-star Alexis Denisof were married in October of 2003. She can currently be seen on the televion show "How I Met Your Mother."