Guerrero performed in Mexico and Japan for several major professional wrestling promotions, and in the United States performed for Extreme Championship Wrestling (ECW), World Championship Wrestling (WCW), and most notably World Wrestling Federation/Entertainment (WWF/WWE). Guerrero's gimmick was that of "Latino Heat", a crafty, resourceful wrestler who would do anything to win a match. His catchphrase became "I Lie! I Cheat! I Steal!" and was used in one of his entrance themes; he partly used this phrase in the title of his 2005 autobiography, Cheating Death, Stealing Life. Despite being a heel for most of his career, he was popular in and out of the ring and was at the peak of his career as a face during 2003–2005, becoming the top wrestler on the SmackDown brand in 2004. He experienced various substance abuse problems, including alcoholism and an addiction to painkillers; these real-life issues were sometimes incorporated into his storylines.
Guerrero spent his early career wrestling in Mexican promotions and forming a popular tag team with Art Barr. After the death of Barr, Guerrero received his first mainstream exposure in the United States in 1995 by joining ECW and winning the ECW World Television Championship. Later that year, Guerrero moved to WCW, where he became WCW United States Champion, WCW Crusierweight Champion and led the Latino World Order. He left WCW in 2000 after the company failed to elevate him to a main event spot.
He moved to WWF with his WCW colleagues Chris Benoit, Dean Malenko and Perry Saturn, who formed a group called The Radicalz. Guerrero went on to win the WWF European Championship and WWF Intercontinental Championship before he was released in 2001 due to addiction issues. After being rehired in 2002, he formed Los Guerreros with his nephew Chavo, winning the WWE Tag Team Championship, and established himself on the SmackDown brand. He climbed to main event status and won the WWE Championship, his sole world championship at No Way Out 2004. He lost the title later that year but remained a popular main eventer until his untimely death on November 13, 2005.
Guerrero left an impact and legacy on the professional wrestling industry as one of the most beloved performers of his generation and an inspiration to many future professional wrestlers. He was posthumously inducted into the WWE, AAA, Wrestling Observer Newsletter and Hardcore halls of fame.