The steely-eyed Serb warmed up with a workmanlike performance in his opener against Frenchman Paul-Henri Mathieu, but was at his devastating best in a 91-minute rout of the 62nd-ranked Harrison.
Bullied on the baseline and broken early in each set, the 20-year-old American scrambled hard to make a contest under the lights at Rod Laver Arena, but surrendered the match when his opponent ripped a searing forehand down the line.
Djokovic will continue his bid for a sixth grand slam title, and fourth at Melbourne Park against Czech veteran Radek Stepanek.
(Reporting by Ian Ransom; Editing by Alison Wildey)
- Sports & Recreation