According to Koslov he decided to take the deal with AAA because he was unhappy with CMLL's direction. Only a few people knew that Koslov had signed with AAA before he made his surprise debut on October 10, 2008 at a AAA Television taping in Querétaro, Mexico. To avoid spoiling the surprise Koslov had covered his face as he travelled to the arena, then stayed out of sight during the show. Koslov's defection to AAA made front-page news on newspapers and wrestling magazines, liking it to the Monday Night Wars between World Championship Wrestling and the World Wrestling Federation. Koslov helped found the stable "D-Generation Mex" together with Sean Waltman and Rocky Romero. On March 20, 2009 Koslov was one of thirteen wrestlers in a "Dome of Death" cage match to qualify for a tournament to establish the AAA Cruiserweight Championship where he qualified for the tournament itself. In the first round Koslov defeated his D-Generation-Mex partner Rocky Romero on April 17, 2009. After the match the two partners hugged without showing any animosity between them. In the semi final Koslov defeated Nicho el Millonario to qualify for the final. On May 21 Koslov defeated Extreme Tiger and Alan Stone to become the first ever AAA Cruiserweight Champion. Alex Koslov's run with the Cruiserweight title only lasted 23 days as he lost to Extreme Tiger at Triplemania XVII on June 13, 2009. Following the title loss Koslov turned "Rudo" attacking his D-Generation-Mex partners after a match. On August 21, 2009, Koslov regained the Cruiserweight championship by winning a five-way elimination match at the 2009 Verano de Escándalo defeating Extreme Tiger, Jack Evans, Teddy Hart and Rocky Romero. On August 30 Koslov lost a six-man steel cage match and as a result was forced out of AAA. Koslov confirmed on his Twitter page that he was done with the company. AAA later vacated his Cruiserweight Championship. On September 26, 2009, at Heroes Inmortales III Konnan kidnapped AAA owner Dorian Roldán and on the October 17 tapings of AAA's television show offered to return him if his father Joaquín reinstated Alex Koslov. Later in the evening, during a match between Marco Corleone and Chessman, a masked man entered the ring and attacked Corleone. The masked man was caught and unmasked to reveal Koslov, whom Konnan then saved by threatening Dorian with violence if Koslov wasn't freed.