The 32-year-old American broke early in each set and was too strong for the German, hitting 31 winners.
"Angelique is a great player and right from the start I knew I had to play really well to be able to win this match," Williams said. "I feel really good."
Williams has been drawn with Agnieszka Radwanska, Petra Kvitova and Kerber in the red group at Istanbul's Sinan Erdem dome. Second seed Victoria Azarenka, Li Na, Sara Errani and Jelena Jankovic are in the white group.
Kvitova defeated Radwanska in straight sets at the conclusion of the day's play.
Belarussian Azarenka beat Errani 7-6 6-2 in the tournament's opening match with the defensively-minded Italian, who led 5-2 in the first set, staying in contention until the tiebreak.
Errani lost that 7-4 and looked to be in pain after suffering a calf injury midway through the second set.
"I was a little rusty at the beginning," Azarenka told reporters. "Overall it was important to take that first set. It was a big turnaround point."
5-Petra Kvitova (Czech Republic) beat 3-Agnieszka Radwanska (Poland) 6-4 6-4
1-Serena Williams (U.S.) beat 8-Angelique Kerber (Germany) 6-3 6-1
2-Victoria Azarenka (Belarus) beat 6-Sara Errani (Italy) 7-6(4) 6-2