In September 1991, Hammer joined World Championship Wrestling with a rock star gimmick. He made his debut for the promotion at Clash of the Champions XVI, where he squashed Terrance Taylor in thirty-nine seconds. He immediately was thrust unto the house show circuit, defeating Taylor in multiple rematches as well as defeating Oz and Cactus Jack. He made his WCW television debut on the October 15 episode of Saturday Night, defeating Paul Lee. Twelve days later, he made his pay-per-view debut at Halloween Havoc, defeating Doug Somers. On November 3, he gained a non-title victory over WCW Television Champion Arn Anderson at a house show in Charleston, West Virginia. Hammer would go on to amass a 42-0 record competing on both house shows and television before finally having his streak ended when he lost a match to Cactus Jack at Clash of the Champions XVII. At Starrcade, Hammer teamed with Big Josh in a losing effort to Steve Austin and Rick Rude.
After briefly continuing his tag team with Big Josh, Hammer returned to singles competition and faced Steve Austin for the World Television Championship on the January 12 episode of Main Event, but was unable to win the title. After the loss, Hammer competed sporadically throughout the rest of the spring (including a brief feud with JT Southern) before returning full-time in August 1992. Hammer would fall to Greg Valentine and Nikita Koloff before his push began to accelerate. In September, he went on a ten match winning streak, defeating Diamond Dallas Page, Vinnie Vegas, and Super Invader. He received a WCW United States Championship shot against Rick Rude on the November 21 episode of WCW Power Hour, but came up short. Hammer teamed with Erik Watts at Halloween Havoc and was victorious against The Vegas Connection. For the remainder of October and November, he was strongly pushed, going 19-2 in a streak that included victories over Tony Atlas, The Barbarian, and Mustafa Saed. He would also team with Brad Armstrong in a brief feud with Page and Vegas.
On the November 21 episode of WCW WorldWide, Hammer was entered into the Jesse "The Body" Ventura Strongest Arm Tournament and defeated Vinnie Vegas. On the December 12 episode, Hammer upset Big Van Vader to advance to the finals against WCW World Heavyweight Champion Ron Simmons. The following week, Hammer defeated Simmons to win the arm wrestling challenge.
Hammer teamed with Sting and was victorious in a tag team match on the November 21 episode of WCW Saturday Night, defeating Rick Rude and Cactus Jack via disqualification. On a November 26 house show in Atlanta, Georgia, Hammer was given a broken nose by Rick Rude during an eight-man tag-team main event match held in a Thunderdome cage match. Despite the injury, he missed no dates and continued to be victorious on the house show circuit. Hammer made his second Starrcade appearance, where he and Dan Spivey defeated Cactus Jack and Johnny B. Badd to qualify for the Battlebowl. In the main event, The Great Muta defeated both Hammer, Spivey and five other wrestlers to win the Battlebowl.
On January 2, 1993, Van Hammer lost to Tony Atlas in the quarterfinals of a tournament for the vacant WCW United States Heavyweight Championship on Saturday Night. A day later, he lost to World Heavyweight Champion Big Van Vader on a house show in Bristol, Tennessee, after which he took time off to have surgery, causing him to miss the Thunderdome match at the Clash of the Champions XXII on January 13. He would be out for a month before returning on the February 9 taping of WCW Power Hour. Hammer continued to be a mainstay on Saturday Night, winning the majority of his matches. At the first-ever Slamboree pay-per-view, Van Hammer lost his match with Sid Vicious in only thirty-five seconds.
Despite the quick loss, Hammer continued to be pushed, defeating Vinnie Vegas on a house show in Louisville, Kentucky on June 3. He was victorious as well against Tommy Angel and Vladimir Koloff as well that month, although he sustained a defeat to Rick Rude. On July 3, Hammer defeated Lord Steven Regal at a house show in Spartanburg, South Carolina. His final WCW match came on July 11 in Tower City, Pennsylvania, when he pinned Wrecking Crew Fury. However due to WCW's lengthy tapings that began that month, he continued to appear much later in the year. On the September 11 episode of WCW WorldWide (taped July 7 in Orlando, Florida) he teamed with 2 Cold Scorpio and Marcus Alexander Bagwell in a losing effort against Sid Vicious and Harlem Heat. His final television appearance came on the November 6 episode of WCW WorldWide (taped July 10 in Orlando, Florida), Hammer attempted to defend his Jesse Ventura's Strongest Arm championship, but was defeated by The Equalizer in the first round.
On July 26, 1993, Hammer received a tryout match for the World Wrestling Federation (WWF) at a WWF Superstars taping in Utica, New York. He worked as a heel, but was defeated. The following day at a Wrestling Challenge taping in Plattsburgh, New York, he was defeated by Damien Demento in another dark match.
Hammer returned to WCW on November 29, 1994, when he was defeated by Dick Slater in a television taping. On the January 21, 1995 episode of WCW Pro (taped on December 4, 1994 in Dalton, Georgia), a challenge was made by Diamond Dallas Page, calling Hammer out to defend his arm wrestling title. Van Hammer made a surprise appearance to accept the challenge and Page faked an arm injury and called it off. One month later, on the February 25 episode of WCW Pro, Page defeated Hammer in an arm wrestling match after Max Muscle interfered.
Hammer returned to WCW in November 1997 under the shortened ring name Hammer, where he was placed in Raven's stable The Flock. Despite being an undercarder, much like the rest of The Flock's members, he was granted a title match against the United States Heavyweight Champion Diamond Dallas Page on the February 23, 1998 episode of Monday Nitro, but was unsuccessful in winning the title. On the March 2, 1998, episode of Nitro, Hammer lost to Page via disqualification in a title rematch.
Hammer began jobbing to several top stars before winning a Loser Leaves The Flock match against fellow Flock member Perry Saturn on a special Friday episode of Nitro on May 4. Despite the win, The Flock attacked Hammer after the match and he was thrown out of the group. In his first match following his expulsion from The Flock, Hammer faced the new United States Heavyweight Champion Goldberg for the title the following night on Saturday Night, but lost. He then abandoned the grunge-related attire he had while with The Flock and became a face by adopting a hippie gimmick. After spending the rest of 1998 and January 1999 jobbing, he became a heel again and changed his gimmick to that an anti-pacifist and returned to using his full Van Hammer name. Following this, he began a short winning streak over the next few weeks before losing to Bam Bam Bigelow on the February 22, 1999 episode of Nitro. Van Hammer quickly rebounded and began another winning streak over the following weeks on Nitro, Thunder, Saturday Night and even on pay-per-view at The Great American Bash on June 13 by defeating Mikey Whipwreck. Hammer's winning streak was ended a few weeks later as he lost to Rick Steiner in a title match for Steiner's World Television Championship on July 11 at Bash at the Beach. On the October 11 episode of Nitro, Hammer lost to Sid Vicious in a match for the United States Heavyweight Championship.
On the May 2, 2000 episode of Thunder, Hammer participated in a 41-man battle royal to determine the number one contender for the World Heavyweight Championship, which was ultimately won by Ric Flair. Soon afterwards, Hammer joined the Misfits in Action and was renamed Major Stash so as to fit in with the stable's military gimmick. However, Stash's tenure with the Misfits was short-lived, as he wrestled what turned out to be his final match in WCW, a losing effort to The Demon on the July 12, 2000 episode of Thunder, as he was released from his contract shortly after.