The seventh seed battled back when down 5-3 in the second set tiebreak and again while at 5-2 in the third set to defeat Wimbledon and US Open finalist Jabeur, who was on debut at the tournament in Fort Worth, Texas.
It marked the fourth career defeat of a top two player by the Belarusian, who joined Maria Sakkari in leading the Nancy Richey Group following the first night's competition.
"I think it's the biggest win of the season for me," said Sabalenka, who reached the semi-finals of the WTA's season finale last year but failed to ignite during a disappointing 2022 campaign.
"She played unbelievable and somehow another miracle happened for me and I was able to win this match."
Commenting on her slow start to the match, Sabalenka added: "I didn't feel welcome on this court. I couldn't understand what was happening, the ball was bouncing too slow for me.
"Then in the second set I kind of calmed down and tried to think what I had to do to win this match."
Sakkari, who secured the last spot at the tournament with a victory at last month's Guadalajara Open, mounted her own upset with a 7-6 (6) 7-6 (4) victory over third seed Jennifer Pegula.
The Greek fifth seed survived two tiebreakers at Dickies Arena for the result, which came as revenge after she lost the final to the American in Guadalajara eight days earlier.
Sakkari said after the match: "I was very aggressive. If you're passive, Jess is just going to make you run - she's going to hit the ball very hard, and it's over."
Next up at the WTA Finals will be world number one Iga Swiatek taking on Daria Kasatkina, while American Coco Gauff faces Caroline Garcia.