Carlo Ancelotti‘s side started poorly at the Power Horse Stadium in Andalusia and fell behind inside the opening 10 minutes courtesy of a clinical finish from former Manchester United youth player Largie Ramazani.
Alaba replaced Ferland Mendy in the 74th minute and curled a sumptuous free-kick past Fernando from 25 yards to seal all three points with his first touch.
Having beaten Eintracht Frankfurt in Wednesday’s Super Cup, Real came into the new La Liga season in a confident mood.
But they were left stunned when Belgian forward Ramazani, who left United in 2020 after coming through their youth ranks, beat the offside trap and fired past Thibaut Courtois to put Almeria ahead.
Fernando continued to frustrate Madrid after the break, denying Benzema with a fine save, but he was eventually beaten in the 61st minute when Vazquez slammed home after the Almeria goalkeeper had kept out Vinicius‘s effort.
Alaba came off the bench and immediately scored from a 75th-minute free-kick to give defending champion Madrid a 2-1 come-from-behind win at promoted Almería.
Best players of the match
Lucas Vazquez squared things up for Real Madrid on the hour after Fernando Martinez had saved from Vinicius Junior.
David Alaba scored Madrid’s second with 15 minutes to go, ensuring the champions survived an opening day scare.