It was Williams' third straight-set victory against her Italian opponent on a hard court this year following wins at the U.S. Open and Toronto Open.
Williams hit six aces in the first set before Schiavone fought back in the second set and broke the American's serve three times. Williams responded with breaks of her own to clinch the victory.
Venus Williams, a wild-card entry, fell to Sabine Lisicki of Germany 6-1, 6-2. Lisicki didn't face a break point and broke Williams three times.
Serena Williams' chances of winning the tournament were boosted by the surprise loss of defending champion Victoria Azarenka on Monday.