In 1998, Vampiro was signed by World Championship Wrestling (WCW). His first match was on the June 29, 1998 episode of WCW Monday Nitro, defeating Brad Armstrong. He would not return to WCW until the March 18, 1999 episode of WCW Thunder, when he defeated Prince Iaukea.
Later that year, he formed a stable with the Insane Clown Posse (ICP) and Raven called The Dead Pool. Even though the stable was short-lived, they gained popularity and had a heated feud with Eddie Guerrero, Rey Mysterio Jr., and Konnan.
Vampiro then feuded with Berlyn. The feud began when Vampiro beat Berlyn in the WCW World Title tournament on Nitro. To exact revenge later in the night, Berlyn cost Vampiro his match against Buff Bagwell and, as a result, Vampiro was eliminated from the tournament. This feud led to the 1999 Mayhem event, where the two fought in a Dog Collar match and Vampiro made Berlyn submit to the Camel Clutch.
Vampiro later began a feud with Oklahoma and "Dr. Death" Steve Williams. Vampiro and Dr. Death then faced off at Starrcade, with the stipulation that if Vampiro won, he would get five minutes in the ring against Oklahoma. After Williams was disqualified, Vampiro had his match with Oklahoma. Surprisingly, Oklahoma was able to mount a bit of offense, until Vampiro took Oklahoma's cowboy hat and then pinned him following the Nail in the Coffin.
In early 2000, he formed an alliance with Sting, as the "Brothers in Paint," after he helped Sting to defeat Lex Luger in a lumberjack match. This did not last long, with Vampiro turning on Sting when he pulled Sting underneath the ring at Spring Stampede 2000. They feuded throughout the spring, with Sting getting the upper hand on Vampiro in nearly all their encounters. This set up the Human Torch match, in which Vampiro won by setting Sting on fire. Vampiro then focused on The Demon due to his defection from the ICP formed stable, The Dark Carnival. He kidnapped his fiancée, Asya. Afterward, he challenged him to a Graveyard Match, which sparked the return of Sting.
Vampiro entered the vacant WCW United States Title tournament, with his first-round opponent being The Great Muta, who Vampiro lost to. Vampiro later joined up with Muta to attack Ernest "The Cat" Miller. Vampiro won his first and only title in WCW with The Great Muta, by defeating KroniK in Vancouver, British Columbia, Canada to win the WCW Tag Team Championships on August 13, 2000. This reign was very short lived, however, as they lost the Tag Team Championships the very next night to Rey Mysterio Jr. and Juventud Guerrera in Kelowna, British Columbia, Canada. Vampiro later turned his back on Muta, setting up a three-way match at Fall Brawl with himself, Sting and Muta, which was won by Sting. Vampiro then took time off.
He returned a month later, where he defeated Crowbar in a hardcore match. Vampiro then challenged Mike Awesome at Halloween Havoc, losing via pinfall after a top rope Awesome Bomb. He was then out with an injury and did not recover before WCW was purchased by the World Wrestling Federation. Thus, his final WCW appearance was on the November 1, 2000 episode of WCW Thunder when he teamed up with Jeff Jarrett to take on Sting and Mike Awesome, which led to a loss for Jarrett and Vampiro after Awesome performed a running powerbomb on Vampiro and pinned him.