The Hardy brothers eventually caught the eyes of the World Wrestling Federation, and after being signed to a contract in 1998, they were trained by former wrestler Dory Funk, Jr. in his Funkin' Dojo with other notable wrestlers such as Kurt Angle, Christian, Test, and A-Train. When the team were finally brought up to WWF TV, they formed the acrobatic tag team called The Hardy Boyz. In 1999, they feuded with Edge and Christian and had a short stint in the stable The New Brood.
The team of Matt and Jeff won the WWE Tag Team Championship on five occasions, ensuring they would be known as one of the most successful tag teams in WWE history. In 2000, Matt and Jeff found a new manager in their real-life friend Lita. Together, the three became known as "Team Xtreme".
Jeff would gain attention for his high risk stunts in the TLC matches in the year 2000 and 2001 (the Hardy Boyz) and 2002 (Jeff Hardy and Rob Van Dam) and made a name for himself as one of the most seemingly reckless and unorthodox WWF performers of his time. In 2001, Jeff would also hold both the WWE Intercontinental and Light Heavyweight Championships.
In early April of 2002 The Hardy Boyz began a feud with Brock Lesnar after Lesnar gave Matt an F-5 on the steel entrance ramp, which led to an angered Jeff seeking revenge on Lesnar. At Backlash 2002 Jeff faced-off against Lesnar in his first televised match. Lesnar dominated Hardy and won the match by knockout. Lesnar and the Hardys would continue to feud over the next few weeks, with the Hardys coming victorious only once by disqualification. At Judgement Day 2002, Lesnar gained the upper hand on the Hardy Boyz before tagging, his partner, Heyman in to claim the win for the team.