Son to Gilbert and Ruby Moore Hardy, Jeff is the younger brother of Matt Hardy. Their mother died of brain cancer in 1987, when Hardy was nine. He developed an interest in motocross aged 12, and got his first bike, a Yamaha YZ-80, at age 13. He had his first race when he was in ninth grade. Hardy played baseball as a child, but had to stop after he crashed during a motocross race, injuring his arm. He also played American football during high school, and played as either a fullback or a linebacker. He also briefly competed in amateur wrestling in high school. He had to stop playing sports in high school, after he was ordered to pick between professional wrestling and playing sports, and he chose wrestling. Hardy cites Sting, The Ultimate Warrior, and Shawn Michaelsas his childhood inspirations to wrestle.

Before gaining prominence in WWE, Hardy performed for the Organization of Modern Extreme Grappling Arts (OMEGA), a promotion he ran with his brother Matt. After being signed by WWE, the brothers worked as jobbers before gaining notoriety in the tag team division, partly due to their participation in Tables, Ladders, and Chairs matches. With the addition of Lita, the team became known as Team Xtreme and continued to rise in popularity. As a tag team wrestler, Hardy is a former six-time World Tag Team Champion and one-time WCW Tag Team Champion.

Apart from his success as a tag team wrestler, Hardy has also had success as a single wrestler. He is a four time Intercontinental Champion, as well as having held the Hardcore, European and Light Heavyweight Championships. He received his first major main event push towards the end of 2007, including challenging for the WWE Championship at the Royal Rumble in 2008.

Moreover, Hardy is involved in motocross, music, and other artistic endeavors. He is currently a member of the unsigned band Peroxwhy?gen.

He has a tattoo of roots that starts on his head, behind his ear, and finishes at his hand. He also has a few other signature designed tattoos, one of which, a dragon, he hid from his father. It was also the first tattoo he got in 1998. He later got tattoos of the Chinese symbols for "Peace" and Health", and also tattoos of fire and a wave. Hardy regards his tattoos as his "artistic impulses". Hardy is very good friends with Shannon Moore, who he has known since around 1987. He is also good friends with Marty Garner and Jason Arhndt.