Harvick led 177 of the 337 laps.
The win earns Harvick an automatic spot in the Championship 4 playoff finale at Homestead.
Despite being out of the playoffs, Ryan Blaney finds himself on the pole at Texas.
"I thought if I could keep him from finishing the corner I could drive back by him", Harvick said.
Joey Logano secured his spot in the Championship 4 last week with a controversial win at Martinsville.
Halfway through the final stage, Keselowski would fall victim to a loose wheel and drop outside the top-10, leaving the usual pack of Harvick, Logano, and Blaney to duke it out.More news: Saints' Thomas pulls celebrates TD with cell phone
Below the cutline after Texas are Kurt Busch (-25 point from fourth), Chase Elliott (-39), Aric Almirola (-57) and Bowyer (-73). Harvick and Blaney would then pit on the next lap, Logano also coming in on trip number 284 "round TMS".
Nevertheless, with the Round of 8 elimination race at Phoenix looming, Busch holds a 28-point edge over his brother Kurt Busch, who is fifth in the Playoff standings after running seventh on Sunday.
Bowyer was involved in first-lap rub with Denny Hamlin.
The third caution of the day occurred when Hendrick Motorsports teammates Jimmie Johnson and William Byron came together on Lap 97, leading to a four-lap yellow flag period.
Harvick was on the inside again for the next restart, but Blaney was able to get by him for the lead.More news: India gets U.S. waiver for development of strategic Chabahar Port in Iran
"They were hard. They were challenging", Blaney said about the restarts. "That was really the only shot we had to beat him, to be honest with you". We're going to take the top and see what happens and obviously it worked out a little bit. "He motored around me".
Truex was forced to start at the back of the field because of a late engine change.
Following the break between Stages 1 and 2, Harvick was again first off pit road and remained in the lead when Stage 2 went green on Lap 93.
"We've been working day after day to make speed", Harvick explained after the checkered flag.
"That last restart I knew I needed to pick the top", Harvick said after the race. However, a three-car incident involving Bubba Wallace, Chris Buescher, and Matt Dibenedetto caused headache for more than just the latter who suffered major damage late in the race.
The only stress for Harvick was lane choice for the overtime.More news: Sane laughs off talk of switch to United