The home side led 1-0 at the interval following a looping header from Portuguese midfielder Tiago.
Atletico's second came 20 minutes from time, when Mario Suarez tapped home from close range.
Read how it all unfolded in Sports Mole's minute-by-minute live commentary of the action below.
Atletico: Moya; Juanfran, Godin, Jimenez, Ansaldi; Tiago, Gabi, Koke; Turan, Mandzukic, Garcia
Espanyol: Casilla; J Lopez, Colotto, Gonzalez, Fuentes; Vasquez, Sevilla, Canas, Alvarez; Garcia, Caicedo