The top seed romped through the opening set in just 26 minutes as Darcis struggled to keep pace with him.
The Serb did not face any break points and dropped only 14 of 45 points on his way to securing the set.
Set two was a different affair altogether though, as Darcis broke the world No 1 to take the advantage at 5-4.
Djokvic held his nerve to level matters and went on to break his opponent again to complete his victory in 88 minutes.
Next up for Djokovic is an encounter with Ukraine’s Alexandr Dolgopolov as he looks to claim his fifth Miami Open crown.