The 51-year-old, who starred opposite Hollywood star Jack Black in the 2006 comedy Nacho Libre, had been performing at the Roundhouse in Camden on Saturday evening.
Organisers of the Lucha Libre show confirmed his death as tributes poured in for the Mexican, whose real name was Cesar Barron.
According to Camden New Journal, Silver King’s co-performers did not initially realise there was a problem after he collapsed following a kick to the side of his body.
He was turned over and counted out but when he failed to recover, a team of medics rushed on stage, the newspaper said.
Fans chanted “Silver, Silver” before the audience was told there would be a short break but the venue was cleared out shortly afterwards, it was reported.
A member of the audience told the Camden New Journal: “It seemed to be part of the show at first but then he didn’t get up – and then the medical team was on the stage.
“Everybody was cleared out and lots of police and ambulances were there.”
According to a description of the show on the Roundhouse’s website, Silver King was due to portray his villainous character Ramses from the film Nacho Libre.
Former WWE star Juventud “The Juice” Guerrera was also listed as one of the performers.
Former WWE stars Chris Jericho, X-Pac and Tommy Dreamer and ex-WCW president Eric Bischoff were among those to pay tribute to Silver King following his death.
X-Pac, whose real name is Sean Waltman, said he was “truly one of the greats”, while Jericho thanked him “for taking care of me and teaching me to become a better worker”.
Silver King joined World Championship Wrestling in 1997 and regularly appeared on its showpiece TV programme WCW Monday Nitro.
His highest profile match was an unsuccessful challenge for the WCW Cruiserweight Championship against Guerrera at Fall Brawl 1998.
He was released by the WCW in late 2000.
Lucha Libre wrestling was first introduced in the early 20th century and is known for its colourful masks, elaborate costumes, acrobatic techniques and high-flying manoeuvres.
