The German took the one spot remaining for the end-of-season tournament, which begins on October 22, with a 6-3 6-1 victory over Austrian wild card Patricia Mayr-Achleitner.
Kerber, who played in Istanbul for the first time last year, said: "I am so excited to be returning to Istanbul for the TEB BNP Paribas WTA Championships.
"The fans last year were amazing and I look forward for the chance to play against the best players in the world."
Serena Williams, Victoria Azarenka, Agnieszka Radwanska, Li Na, Petra Kvitova, Sara Errani and Jelena Jankovic have also qualified, while Maria Sharapova pulled out with a shoulder injury.
Second seed Sloane Stephens suffered a disappointing 6-7 (3/7) 6-4 7-5 loss to Swiss Stefanie Voegele, who will meet Ana Ivanovic in the last four.
The third seed recovered from an early break down in the second set to beat Dominika Cibulkova 6-2 6-4.
Kerber plays fourth seed Carla Suarez Navarro, who cruised to a 6-1 6-3 victory over fifth seed Kirsten Flipkens.