Dragón made his debut for World Championship Wrestling (WCW) in 1996. He was quickly pushed into the lime-light of the WCW Cruiserweight division with Sonny Onoo as his manager. He made his WCW pay-per view debut in 1996's Hog Wild against Rey Misterio, Jr. for the WCW Cruiserweight Championship, but lost. He got back the win at WCW World War 3, when he returned to WCW. He then feuded with Dean Malenko for the WCW Cruiserweight Title, which he won at Starrcade 1996.
Dragon later dropped the WCW Cruiserweight Title back to Malenko, but his stock was rising as he won the WCW World Television Championship from Prince Iaukea, but lost it to Steven Regal. He then turned face by dropping Onoo as his manager and won back the WCW World Television Title from Regal before losing to Alex Wright at Clash of the Champions XXXV. He would then win the WCW Cruiserweight Title one last time from Eddie Guerrero, before losing the title on the first WCW Thunder to Juventud Guerrera. He then suffered an arm injury in 1998 that required surgery. He would leave WCW soon after.
In the spring of 2003, he signed with World Wrestling Entertainment. He made his WWE debut in dark match victories against Rico, Crash Holly and Shannon Moore as they debuted a series of video packages hyping the debut of Dragon on SmackDown!. He made his WWE television debut at Madison Square Garden on June 26, 2003 episode of SmackDown! in a match with Shannon Moore.
Throughout the summer, he competed in a tournament for the WWE United States Championship, beating Jamie Noble, but losing to eventual winner, Eddie Guerrero. He quickly rebounded by beating Kanyon in a WWE Heat match taped before Vengeance. He then wrestled on WWE Velocity for the next few weeks, leading to a match with Rey Mysterio on SmackDown. Dragon won the match only after Tajiri interfered and showed respect to Dragon due to their Japanese heritage. The next week, Dragon teamed with Mysterio to take on Tajiri and Nunzio. After this match, he was not seen on SmackDown! for several months until the build for the Cruiserweight Open at WrestleMania XX. At the event, Dragon participated in the match. After the match, he faced Chavo Guerrero and Nunzio in his last WWE matches. On April 22, 2004, WWE announced that he was released from his WWE contract.