Jesse McCartney was born April 9, 1987 in Westchester County, New York. He began performing onstage in local musicals at the age of 7. Jesse McCartney made his Broadway debut in a production of The King and I at age 10. He also appeared in a production of A Christmas Carol starring Roger Daltrey of the Who. After a stint singing on record with the children's group Sugar Beats, Jesse McCartney was asked to join the boy band Dream Street.

Jesse McCartney joined Dream Street in 2000 when he was only 12 years old. The group's first self-titled album, released in 2001, sold well, but by 2002 the group was breaking up. Jesse McCartney has described being a member of Dream Street as a good experience in preparation for his solo career.

Cook dibesarkan di Blue Springs, Missouri.Kedua orang tuanya adalah Beth (nama gadisnya Frye) dan Stan Cook.Adik laki-laki Cook, Andrew, adalah sarjana pendidikan sekolah dasar dari University of Central Missouri,dan kakak laki-lakinya, Adam, hidup di Terre Haute, Indiana bersama istri dan anak-anaknya.Beth dan Stan bercerai ketika Cook masih kecil; ibunya menikah lagi dan sekarang berganti nama menjadi Beth Foraker, sementara ayahnya pindah ke Indianapolis, Indiana.

Minat Cook terhadap musik mulai sejak ia masih kecil. Ia memperoleh gitarnya yang pertama pada usia 2 tahun. Ia mulai bernyanyi di kelas dua, ketika guru musik di SD-nya memberikan kesempatan kepadanya untuk bernyanyi solo di pertunjukan paduan suara sekolah. Ia kemudian tampil di hampir setiap acara Natal dan PTA.Ia juga berpartisipasi dalam paduan suara dan ekstrakulikuler teater di SMP dan SMA. Di Blue Springs South High School, ia tampil dalam drama-drama musikal, seperti The Music Man, West Side Story, and Singin' in the Rain.