Spike debuted in Extreme Championship Wrestling on September 21, 1996, as a fan favorite and as a part of the Dudley family. In his debut match, Spike teamed with his storyline brother Bubba Ray Dudley to defeat The Erotic Experience (GQ Gorgeous and Pat Day). He made his televised debut in ECW on the October 1 episode of Hardcore TV. His in-ring persona was that of the "runt" of the family. His initials LSD and finishing move, the Acid Drop were both drug references and, at times, he would stare at his hands waving in front of him as if he were on a trip. At Crossing the Line Again on February 1, 1997, Bubba turned on the Dudley family by aligning with D-Von Dudley and hitting a Dudley Death Drop on Spike and forming the tag team The Dudley Boyz. This also resulted in Spike becoming the first recipient of the Dudley Death Drop or 3D. As a result, Spike began a lengthy on-and-off scripted rivalry with them which continued for two years.
Spike would lose to Dudley Boyz' ally Axl Rotten on a few occasions at Winter Blowout and CyberSlam. During the summer of 1997, Spike teamed with Mikey Whipwreck and got involved in a mini feud with PG-13, which resulted in Dudley and Whipwreck defeating PG-13 at Heat Wave. Dudley's first high-profile feud began with Bam Bam Bigelow when Dudley defeated Bigelow to score an upset win at Born to be Wired. He quickly gained the nickname "The Giant Killer", as he would be booked to score quick wins against larger and heavier opponents. Dudley lost to Bigelow in a rematch in his pay-per-view debut at Hardcore Heaven. At As Good as it Gets, Dudley lost to Bigelow in a match. The match was notable for a very interesting moment in not only Spike's career but in ECW history in general, in which Bigelow threw him from the ring over the top rope and into the crowd. The fans caught him and proceeded to body surf him around the ECW Arena.
Teaming with multiple people, including Tommy Dreamer, The Sandman, New Jack, and Nova, he defeated them to win the ECW World Tag Team Championship with his partner Balls Mahoney on two occasions in 1999.
He was also in the main event on some occasions, such as the 2000 Guilty as Charged pay-per-view, where he faced Mike Awesome for the ECW World Heavyweight Championship, in a losing effort. During the match, however, he injured his knee, and after aggravating the injury in subsequent matches with Awesome and Lance Storm, was forced to take several months off to recuperate. He returned in June 2000 as the ECW Commissioner and returned to in-ring action at the November to Remember event of that year, relinquishing his role as commissioner. Spike stayed with ECW until it folded in 2001.
Dudley joined the World Wrestling Federation (WWF) in 2001, aligning with his half-brothers, Bubba Ray and D-Von. With his brothers in the middle of a three-way feud for the WWF Tag Team Championship with the Hardy Boyz and Edge and Christian, Dudley frequently battled with Lita and Rhyno to try and help their respective team win (Lita managed The Hardy Boyz while Rhyno managed Edge and Christian). Notably, all three were heavily involved in the Tables, Ladders and Chairs (TLC) match at WrestleMania X-Seven. Although Dudley inadvertently saved Lita from being taken out by Rhyno, Dudley later took a hard chair shot to the head from Lita (who was later taken out by Bubba Ray and D-Von) and was then taken out by Jeff Hardy when he performed a Swanton Bomb off a 20-foot ladder and landed on two parallel tables with Rhyno on one and Dudley on the other, with Jeff mostly landing on Dudley's table.
After WrestleMania, The Dudley Boyz began a feud with The Holly Cousins. During this time, Dudley began a relationship with Molly Holly, which led to the Dudleys turning on him and putting Holly through a table. On June 14, 2001, Dudley was given his first opportunity at the WWF Championship, in a losing effort against Stone Cold Steve Austin. During The Invasion, Dudley remained loyal to WWF, despite being an ECW Original. It was during The Invasion that his relationship with Molly came to an end when she turned on him, aligning herself with The Alliance.
Between May 2001 and January 2002, Dudley formed short-lived tag teams in an attempt to defeat his brothers. On the January 7, 2002 edition of Monday Night Raw, Dudley and Tazz defeated The Dudleys for the WWF Tag Team Championships, and successfully retained them at the Royal Rumble. Dudley next entered the Hardcore Championship picture, winning the championship eight times, including at WrestleMania X8 (though he never held the championship for more than a day, due to the "24/7 rule.") He also defeated William Regal for the European Championship on April 8, 2002, and held the championship for a month before losing it back to Regal.
As 2002 went along, Spike and Bubba began to team together again and feuded with The Un-Americans while also pursuing the World Tag Team Championship. By the end of the year, D-Von had rejoined his brothers, and they feuded with 3-Minute Warning. Dudley was injured after a missed spot during a 10-man tag match on Raw in September 2003. La Résistance threw Dudley to the outside but Dudley missed the table that he was supposed to crash through. After some time away from the ring, Spike returned and defeated René Duprée to get revenge for the injury.
In 2004, Dudley was drafted to the SmackDown! brand, where he immediately began challenging for the WWE Cruiserweight Championship. On July 27, 2004, he defeated Rey Mysterio for the championship with interference from his brothers, thus turning into a heel. He then began to wrestle as the "boss" of the Dudley Boyz. The Dudleys defeated Mysterio, Billy Kidman and Paul London in a six-man tag team match at SummerSlam. He continued to defend his championship throughout the year, before eventually losing the Cruiserweight Championship to Funaki at Armageddon.
He made his last appearance with WWE at ECW One Night Stand on June 12, 2005, helping the Dudleys win their tag team match. At the event, Spike was dressed like his old ECW character (tie-dyed shirt and overalls) but still portrayed his WWE "Boss" character. Dudley was released from his WWE contract on July 5, 2005, along with seven other wrestlers. Bubba and D-Von also departed the company after ECW One Night Stand.