The Spaniard won nine of the first 10 games as he wrapped up victory in one hour and 12 minutes.
Dimitrov was able to bring the second set back on serve at 3-3 but Alcaraz then escaped two break points in the seventh game before sealing victory.
The Paris Masters is the final regular ATP Tour event of the season, before the ATP Finals get under way in Turin on 13 November.
Aiming to win his third ATP Masters 1000 title of the year following successes in Miami and Madrid, Alcaraz is guaranteed to be the top seed in Turin after world number two Rafael Nadal suffered a second-round defeat by American Tommy Paul.
Should he triumph in Paris, the teenager would secure the year-end world number one ranking before his debut appearance at the Finals.
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