After the release of On My Way Here Aiken left RCA and later signed with Decca Records. His first album with Decca, Tried and True, was released June 1, 2010.

In the years following his American Idol appearance, Aiken has launched nine tours, authored a New York Times best-selling book Learning to Sing: Hearing the Music in Your Life with Allison Glock, and was the executive producer for a 2004 televised Christmas special, A Clay Aiken Christmas. He has been a frequent talk show guest, particularly on The Tonight Show and Jimmy Kimmel Live. He appeared as a guest star on Scrubs and participated in comedy skits on Kimmel, Saturday Night Live and 30 Rock.

Aiken created the National Inclusion Project (formerly the Bubel/Aiken Foundation) in 2003, accepted a UNICEF ambassadorship in 2004, and in 2006 was appointed for a two-year term to the Presidential Committee for People with Intellectual Disabilities.

Aiken made his Broadway debut playing the role of Sir Robin in Monty Python's Spamalot in January 2008. His run ended in May but he rejoined the cast as Sir Robin in September and remained through January 4, 2009.

Clay Aiken was born and raised in Raleigh, North Carolina. As a young boy, Aiken sang in the Raleigh Boychoir, and as a teenager, he sang in school choirs, church choir, musicals and local theatre productions. After high school, he sang lead with a local band, Just By Chance, cohosting and performing with the band at "Just by Chance and Friends" shows in Dunn, North Carolina. He was also MC and performer at the Johnston Community College Country Showcase in Smithfield, and at the North Carolina Music Connection and Hometown Music Connection shows in Garner and Benson. He performed the national anthem numerous times for the Raleigh IceCaps and the Carolina Hurricanes hockey teams.

Three demo albums of Aiken's vocals were created before American Idol with the aid of studio time given as a birthday gift by his mother: a cassette called Look What Love Has Done (by Clayton Grissom), a cassette and CD entitled Redefined (by Clayton Aiken), and a CD that combined some songs from each of the previous demos: "Look What Love Has Done, Vol 2" (by Clay Aiken). Estranged from his birth father Vernon Grissom and with his mother's and grandfather Alvis Aiken's permission, at the age of 19 he legally changed his surname from Grissom to Aiken.

Aiken attended Raleigh's Leesville Road High School and took courses at Campbell University before enrolling at the University of North Carolina at Charlotte. He found his interest in special education while directing YMCA children's camps as a teenager, and at age 19, he served as a substitute teacher for a classroom of students with autism at Brentwood Elementary School in Raleigh. While attending college in Charlotte, he took a part-time job as an assistant to a boy with autism, and it was this child's mother, Diane Bubel, who urged him to audition for American Idol. Although his American Idol activities temporarily delayed his academic pursuits, Aiken completed his course work while on tour and graduated with a bachelor's degree in special education in December 2003.

On August 8, 2008 Aiken announced, on his personal blog, the birth of his son in North Carolina: "My dear friend, Jaymes, and I are so excited to announce the birth of Parker Foster Aiken". The child's mother, Jaymes Foster, is the sister of record producer David Foster and the executive producer of Aiken's last three albums on the RCA label. "The little man is healthy, happy, and as loud as his daddy," Aiken wrote. "Mama Jaymes is doing quite well also." Aiken said in his book, Learning to Sing: Hearing the Music in Your Life, that "It's a Southern tradition to be given your first name from your grandmama's maiden name." His middle name came from his paternal grandmother's maiden name; using instead the married surnames of their mothers, he and Foster followed that tradition in choosing their son's name.

After several years of public speculation, Aiken disclosed that he is gay in a September 2008 interview with People magazine. In April 2009, Aiken was honored by the Family Equality Council advocacy group at their annual benefit dinner in New York City.

Aiken had filled out an application to participate in the reality show Amazing Race when a friend of his insisted that he try out for American Idol instead. Television viewers first glimpsed Aiken during the audition episodes at the beginning of American Idol's second season. The show's judges first saw Aiken as a nerdy type unlikely to be any kind of idol, but after hearing him sing Heatwave's "Always and Forever" decided to advance him to the next round. The clip of the judges' surprise during this audition performance was replayed many times over the course of the competition.