Williams came into the finals after injuries forced her out of her previous two outings and following Russian official Shamil Tarpischev’s disparaging comments about her and sister Venus.
The top-ranked Williams was shaky in her opening service game, saving two break points, but still took a 4-1 lead. Ivanovic got back on serve but lost the first set when she double-faulted at 15-40 in the final game one of her seven double-faults.
Ivanovic broke Williams to open the second set but the American immediately broke back and took control, improving her career record against the Serb to 8-1.
Before the WTA Finals, Williams retired from the China Open and Wuhan Open because of illness and a left knee injury that had her in doubt for Singapore. But with the win over Ivanovic, she closed in on Martina Navratilova’s record of 21 straight wins at the season-ending tournament.