In 1993, Snow competed in the World Wrestling Federation (WWF) as a jobber, losing to Marty Jannetty and The Undertaker under the name Steve Moore.Snow made his Extreme Championship Wrestling (ECW) debut against The Tazmaniac, losing via pinfall on February 4, 1995. Snow also faced Chris Benoit in a 15-minute match.
Snow began working for the WWF when he signed a contract in August 1995. He wrestled under numerous gimmicks in the WWF, such as Avatar (a luchadore-esque ninja gimmick) with Snow coming to the ring unmasked, putting on a mask to wrestle, then removing it afterwards). During his short run, Avatar teamed with Aldo Montoya. Snow's WWF debut as Avatar took place on the October 23, 1995, episode of Monday Night Raw, defeating Bryan Walsh. One month after his debut, he was supposed to be the third man for The Underdogs team at Survivor Series, but was replaced by Bob Holly for unknown reasons. His two final matches as Avatar were against Sycho Sid and 1-2-3 Kid in a tag team match, partnered with Aldo Montoya, while his final match was against Isaac Yankem. On February 20, 1996, Snow wrestled as Shinobi, a "ninja assassin" hired by Jim Cornette to dispose of Shawn Michaels, who defeated Shinobi in quick fashion.
Snow received his first mainstream exposure with the WWF as Leif Cassidy, the tag team partner of Marty Jannetty in February 1996. The duo were promoted as The New Rockers, a throwback to the original Rockers team of Jannetty and Shawn Michaels. Eventually, Jannetty left, and Cassidy was reduced to jobbing for mid-carders in January 1997. In the late 1990's, WWF and ECW began to cross-promote their organizations; Snow was one of the wrestlers sent to Extreme Championship Wrestling (ECW). His last appearance in WWF in September 1997 was a loss to Tiger Ali Singh at WWF One Night Only.
Cassidy found success back in ECW, billed once again as Al Snow. Snow developed a new character gimmick; he got the idea to portray an individual with a schizophrenic disorder using the head as a prop for projection.
In the storyline, Snow, upset at his lot in life, asked Cactus Jack what he had to do to get anywhere in wrestling. Snow started coming to the ring with a mannequin head (with the words "Help Me" written backwards on its forehead, an action Snow himself began to do) whom he talked to as if it were a real person, which prompted ECW crowds to chant "We want Head". The biggest match of his ECW career came when he wrestled for the promotion's World Heavyweight Championship, losing to Shane Douglas at Wrestlepalooza in 1998.
Snow was then recalled to the WWF, where he continued his gimmick of talking to "Head," creating some of the more memorable humorous skits of "The Attitude Era" including fighting himself in a hardcore match (which he won by putting himself through a table) and his short lived comedy tag team with Steve Blackman.
At WrestleMania XV, Snow lost a WWF Hardcore Championship triple threat match involving Hardcore Holly and Billy Gunn. During the summer of 1999, at the conclusion of a storyline where Head was impaled with a spike by Prince Albert, Snow replaced Head with a chihuahua named Pepper, who he claimed talked to him. A variety of segments were broadcast showing Snow's interactions with the dog, including bringing Pepper to the ring to either "participate" in matches or be held by the broadcast team. This led to a storyline where Big Boss Man kidnapped Pepper. Boss Man agreed to return the dog if Snow defeated him in a match for the Hardcore title; however, after losing the match he reneged and kept the dog. Later, in a segment on SmackDown, Boss Man invited Snow to his hotel room to discuss the situation, before serving Snow dinner which was then revealed to be Pepper. The feud culminated at a "Kennel from Hell" match at Unforgiven, which consisted of a regular cage which was surrounded by a Hell in a Cell structure, with "a trained pack of wild dogs" in between the two, and the objective was to escape both cages without being attacked by the dogs. Al Snow won the match.
Snow would later team with Mick Foley and became the WWF Tag Team Champions with him for a short amount of time, but turned heel by betraying him due to Foley's jokes about him in his autobiography, Have A Nice Day, and his growing jealousy of Foley's tag team partner, The Rock. He would later turn face again due to fan reaction. Snow was often the butt of Foley's jokes during Foley's tenure as the Commissioner in 2000.
In early 2000, he began to team with Steve Blackman as an "odd couple" tag team called Head Cheese (the "cheese" part being given various explanations, including Snow's claim that Blackman was a voracious eater of cheese and later his attempt to force him to wear a Green Bay Packers "Cheesehead" hat). At WrestleMania 2000, the two suffered a loss against Test and Albert. Also in the same year, Snow won the European Championship from Perry Saturn. He then began a tongue-in-cheek gimmick of entering the ring to various European countries' native music, with his theme song sung in the language of the country, and wearing attire which would suit the stereotype of that country. This continued until he lost the title to William Regal.
In 2001, Snow tried to rally support from the fans to vote for him as the new Commissioner of the company following Foley's on-screen firing by Vince McMahon in December 2000. By March 2001, a match was set up between Snow and Regal to determine the new Commissioner, which resulted in Regal winning. Snow then took some time off from the ring in order to commit more time for the reality show Tough Enough. He made his return to the ring in October 2001, during the Invasion era and challenged Christian for the European Championship at Survivor Series, which he lost.
Snow's last championship reign came on March 11, 2002, when he defeated Goldust to win his last Hardcore Championship. He lost the title to his former Tough Enough student, Maven, a few days later. He was drafted to SmackDown! as part of the 2002 Brand Extension, where he teamed up with Maven. After taking time off again for another season of Tough Enough, Snow returned as a member of the Raw roster and eventually became a commentator for Sunday Night Heat alongside Jonathan Coachman. When Coachman sided with Eric Bischoff, Snow followed suit, turning heel. The two feuded with Jim Ross and Jerry Lawler, and briefly replaced them at the Raw announce table after a victory at Unforgiven in 2003. When Tough Enough IV came to SmackDown!, Snow was on the scene and turned face once again.
In September 2004, Snow left Sunday Night Heat as a commentator and went to Velocity. In June 2006, Snow returned to wrestling full-time as a member of the new ECW brand. His first appearance in the new brand was in the WWE versus ECW Battle Royal at the "WWE vs. ECW Head to Head" special, where he was accompanied by Head. He was eliminated from the match. On the June 13, 2006 debut of ECW on Sci-Fi, Snow participated in an Extreme Battle Royal, which was won by Sabu. Over the next six months, he was used sporadically, mostly as a jobber, losing to people such as Test and Kevin Thorn.
After a long hiatus from television, Snow was released in February 2008.