Collecting 43% of fans' votes, Guaita pipped Gary Cahill to being named in first place, with the centre-back receiving the selection from 36.5% of Eagles.
The Spanish shot stopper kept his third consecutive clean sheet against the Hornets, helping to secure Palace seven points from three impressive matches.
Palace have now kept the second most clean sheets in the Premier League, only one behind Leicester City. Guaita has kept all of them - six - making him the 'keeper with the second most top flight shut-outs.
Of the last three games, Guaita has been named Man of the Match twice and picked up the ManBetX Player of the Month trophy for his display in November.