Valdés participated in more than 50 Mexican films, specializing in hyperactive underdog characters. He is most remembered, however, for playing Don Ramón in the hit television show El Chavo del Ocho. Show creator and main star Chespirito was a fan of Valdés, and he thought Valdés would make a perfect fit to play Don Ramón, who had a daughter (Chilindrina, played by María Antonieta de las Nieves), a person who had romantic interest in him (Doña Clotilde, played by Angelines Fernández) and a neighbor who slapped him across the face on every show (Doña Florinda, played by Florinda Meza). The Chavo character played by Gómez would sometimes call Valdés' character "Ron Damón", transposing the initial letter of both words, as some children would do; as a result, Valdés' character was known by both monikers.
Valdés also appeared prominently on Chespirito's other hit show, El Chapulín Colorado, usually as Chapulín's antagonist, the famous Tripaseca. In some episodes he played Super Sam, an English-speaking, money-armed superhero mocking both Uncle Sam and the relatively wealthy economical situation of Americans when compared to the average Latin American and also a critic of the American colonialism.
Both El Chavo and El Chapulín became major international hits across Latin America, Spain, the United States and other non-Spanish speaking countries, giving their entire cast international fame. Ramón Valdés was no exception, he would be identified as Don Ramón (or as "Ron Damón") at many different countries he visited.
In 1978, he quit Chespirito's productions, but he returned to television a few years later, with fellow Chavo del Ocho and Chapulín Colorado cast member Carlos Villagrán in Federrico. Federrico found little success, however, and Ramón Valdés returned to work with Chespirito for a brief time in 1981. Valdés and Villagrán were replaced by Raul "Chato" Padilla, a more experimented actor who played Jaimito The Postman in the remaining Chavo del 8 episodes.
Valdés also owned a circus, participating in circus acts.
Ramón Valdés is regarded as one of the greatest Mexican comedians. His character in "Chavo del Ocho" was considered as the funniest in the show, according to fan research. His popularity is still noticeable in Latin America, judging by the existence of Argentine ska band "Ron Damón", as well as a song of the same name by Chilean band Los Mox, the popularity of a graph parodying the famous Alberto Korda photograph of Che Guevara- but with Don Ramón's likeness- and the existence of t-shirts showing the character and stating: "Ron Damón is punk!" or Listen to The Ramones, with a picture of Don Ramón wearing headphones.