A tense first half was followed by an enthralling second, in which the visitors netted four goals while holding the hosts to just one, scored from the penalty spot after Guidetti was brought down by Courtois inside the 18-yard box.
After the restart, Alaves were unable to keep things tight as Real Madrid’s individual quality shone through, with Benzema proving decisive inside the opposition’s penalty area.
In an overall positive showing from Ancelotti’s side, Modric looked his creative best despite his age, and Hazard made his mark despite being withdrawn just after the hour.
Alaves showed promising signs early on, but they will need to improve their attack if they are to avoid relegation.