Amy Lou Adams was born in Vicenza, Veneto, Italy, to American parents Kathryn (Hicken) and Richard Kent Adams, while her father was a U.S. serviceman. She was raised in a Mormon family of seven children in Castle Rock, Colorado, and has English, as well as smaller amounts of Danish, Swiss-German, and Norwegian, ancestry.
Adams sang in the school choir at Douglas County High School and was an apprentice dancer at a local dance company, with the ambition of becoming a ballerina. However, she worked as a greeter at The Gap and as a Hooters hostess to support herself before finding work as a dancer at Boulder's Dinner Theatre and Country Dinner Playhouse in such productions as "Brigadoon" and "A Chorus Line". It was there that she was spotted by a Minneapolis dinner-theater director who asked her to move to Chanhassen, Minnesota for more regional dinner theater work.