Alyson Hannigan net worth: Alyson Hannigan is an American actress who has a net worth of $18 million dollars. Alyson Hannigan is probably most famous for her roles as Willow Rosenberg on the cult classic television series Buffy the Vampire Slayer, Michelle Flaherty in three American Pie films, and Lily Aldrin on the CBS sitcom How I Met Your Mother. Alyson was born in Washington, D.C., on March 24, 1974. Alyson Hannigan earns a salary per episode of $225,000 on How I met Your Mother. She is marreid to fellow actor Alexis Denisof since 2003 and they have two children together.