Two first-half goals helped los Colchoneros go into the second leg of the quarterfinal with a healthy cushion and a clean sheet at the Vicente Calderon on Thursday night
Radamel Falcao opened the scoring early on before Filipe Luis doubled the lead midway through the first 45 minutes, and a fine performance from on-loan goalkeeper Thibaut Courtois ensured that the score remained that way for the rest of the match.
The hosts named a very strong side for what might be their best chance at attaining silverware this season. Star striker Falcao propelled Atletico to a perfect start, too, as Raul Garcia's whipped cross is thumped into the back of the net by the former Porto forward.
On 23 minutes, after a quiet spell at the Vicente Calderon, Filipe Luis sparked the stadium back into life with a powerful finish, punishing the visitors for failing to clear a Mario Suarez free kick.
Courtois, on loan from Chelsea for the second season running, was on hand to deny the visitors any sniff of a comeback. On 30 minutes he pulled off a wonderful double-save to deny Betis a route back into the clash.
And, after an impressive first half, the goalkeeper blocked superbly five minutes into the second half from a dangerous Jorge Molina shot inside the penalty area.
Betis had the majority of possession in latter 45 minutes but were unable to convert their chances, and Atletico's tight defence deserves acknowledgement for securing the cup win and keeping a clean sheet in the process.
The victor of the two-legged cup clash will face either Sevilla or Real Zaragoza in the semifinals, and los Colchoneros will be favourites to make it into the penultimate round of the competition after this result.