The son of well-known surfer Jeff Johnson, Jack was born and raised on the North Shore of Oahu, Hawaii. He began to learn how to surf at the age of five. At seventeen he became the youngest invitee to make the finals of the Pipeline Masters, one of surfing's most prestigious surfing events, on Oahu's North Shore. One week later, however, his stint as a professional surfer ended when he suffered a surfing accident at the Pipeline that put more than 150 stitches in his forehead and removed a few of his teeth; this later became the inspiration for the song "Drink the Water". He appeared as a surfer in The Endless Summer II in 1994.
Jack Johnson graduated from Kahuku High School in Oahu. He would later attend the University of California, Santa Barbara (UCSB), and graduated in 1997 with a B.A. in Film Studies. While Johnson learned the guitar at the age of 8 and started songwriting at the age of 12, his passion for music grew when he played rhythm guitar for the band Soil (not to be confused with the heavy metal band of the same name) in college. In 1994, Zach Gill's band, Django Reinhardt, released a CD that quickly made Django a favorite band of the Isla Vista party scene at UCSB. Django was the rival of Jack Johnson's band Soil, but Gill and Johnson developed a strong friendship, eventually becoming bandmates in later years. While with Soil at UCSB, Johnson opened for then relatively unknown acts such as Sublime and Dave Matthews with far from sold out crowds at the venues.
Johnson credits his songwriting influences as Bob Dylan, Jimi Hendrix, Radiohead, Otis Redding, G. Love and Special Sauce, Ben Harper, Sublime, The Beatles, Bob Marley, Neil Young, and A Tribe Called Quest. Johnson names Jimi Hendrix as his all-time favorite guitarist.