Underwood graduated from Checotah High School in 2001 as salutatorian. After high school, she moved on to Northeastern State University in Tahlequah, where she graduated magna cum laude in 2006 with a bachelor's degree in mass communication and an emphasis in journalism. Underwood is a member of the Alpha Iota chapter of Sigma Sigma Sigma sorority, and a tribal member of Muscogee Creek Nation of Oklahoma. For two years during the summer, she performed in Northeastern's Downtown Country show in Tahlequah. She also competed in numerous beauty pageants at the university and was selected as Miss NSU runner-up in 2004.
In the summer of 2004, Underwood auditioned for American Idol in St. Louis. When her initial audition aired in January 2005, many people predicted she would win the competition. On March 22, 2005, Underwood sang a powerful rendition of the number one 80's rock hit Alone by Heart and the notoriously hard-to-please judge Simon Cowell predicted that Underwood would win the competition and outsell all previous Idol winners. Underwood was the second winner never to have been voted in the bottom three. While on the show, Underwood gained a loyal fan base known as "Carrie's Care Bears." Interestingly, she is in the same sorority (Sigma Sigma Sigma) as Linda Denham, the creator of the original Care Bears franchise.
On May 25, 2005, Underwood was crowned the winner of American Idol (Season 4) beating out Bo Bice. On December 7, 2006, Underwood's album "Some Hearts" received 4 Grammy nominations. Underwood received two Grammy awards for "Best New Artist", and "Best Female Country Vocal Performance" while "Jesus, Take the Wheel" received nominations for "Best Country Song" and "Song of the Year".
Underwood's nomination marked the first time that an American Idol winner or contestant had been nominated in the "Best New Artist" category. The award ceremony was held on February 11, 2007 at Staples Center in Los Angeles, California. She also sang alongside Grammy nominees Rascal Flatts. On March 24, 2007, Underwood was featured as the musical guest on Saturday Night Live with host Peyton Manning. Underwood performed her hit singles "Before He Cheats" and "Wasted", help bringing the show's highest ratings in the last 10 months. She became only the tenth country music star to perform on the show (preceded by Garth Brooks, Randy Travis, Dolly Parton, Faith Hill, The Charlie Daniels Band, Dixie Chicks, Willie Nelson, Johnny Cash and Keith Urban). She is the third American Idol contestant to appear on the show (preceded by Clay Aiken and Kelly Clarkson).