Juan Pierre's two-out RBI double in the 10th lifted the White Sox to a 7-6 victory over the Royals in the second game after Betancourt tied it with a two-out single in the ninth.
In the first game, Betancourt hit a grand slam in the seventh inning, then delivered a two-out single in the 11th that gave the Royals a 6-5 win over the White Sox. His two-out RBI single in the ninth inning of the second game scored Mitch Maier, who had tripled, to tie it.
"It was an extremely long day, but they never let up for a second until the final out," Royals manager Ned Yost said. "Yuney again was Mr. Clutch there in the ninth inning, driving in the tying run."
Gordon Beckman led off the 10th inning with a single, advanced to second on Ramon Castro's sacrifice bunt and scored the game-winning run on Pierre's double to right.
"A split is not what we wanted, but we battled back," Pierre said. "You don't have time for doubts after Kansas City tied it. You've just got to play. That's the kind of mentality we have."
The two teams played 21 innings, lasting 6 hours, 31 minutes, plus a five-minute delay in the second game when a bank of lights went out.
Tony Pena, who had not started since 2005 in the minors, was pushed into an emergency start for the White Sox after a rain out Friday. He went a career-high seven innings, retiring the last 12 batters he faced, and allowed four runs on five hits.
"To come out and pitch very well when we most needed, he was fun to watch," White Sox manager Ozzie Guillen said.
Once he left, however, the bullpen could not hold a two-run lead.
The Royals began the fourth with five straight hits for a four-run inning. Billy Butler had a two-run single, while Wilson Betemit's double scored Gregor Blanco with the first run. Mitch Maier's sacrifice fly scored Butler with the final run of the inning.
Betancourt's third grand slam of the season tied a Royals record set by Danny Tartabull in 1988. Betancourt and Alex Rodriguez are the only major leaguers with three slams this season. Wilson Betemit drew a leadoff walk from rookie Chris Sale (0-1) in the 11th, moved up on Alex Gordon's sacrifice and stopped at third on Mike Aviles' two-out single. Betancourt's single to center won it.
"I just told Gibby when Willie was up there if we can find some way to get Yuney up to the plate this inning, I think something good will happen," Yost said. "Sure enough I was a fortune teller. He's hot as a fire cracker."
Jesse Chavez (2-1), the fourth Kansas City pitcher, worked two scoreless innings to earn the victory.
White Sox starter Freddy Garcia held the Royals to four hits and one run -- Betemit's leadoff homer in the fifth -- through six innings.
In the seventh, Garcia walked Billy Butler and gave up two-out singles to Willie Bloomquist and Aviles. Sergio Santos relieved Garcia and gave up Betancourt's grand slam on his second pitch. The White Sox threatened in the 10th, but pinch-runner Brent Lillibridge was thrown out at the plate trying to score on Carlos Quentin's double to right-center.
Royals right-hander Phil Humber, making his first big league start since Sept. 26, 2007, with the New York Mets, allowed five runs on nine hits, while striking out six in 5 2/3 innings.
Humber had not pitched since a relief appearance on Aug. 10. He was primarily a starter this season with Triple-A Omaha.
Pierre, who leads the majors with 49 stolen bases, led off the White Sox third with an infield single, swiped second and scored on Omar Vizquel's single. The White Sox made it 2-1 in the fifth when Pierre's single scored A.J. Pierzynski.
The White Sox upped their lead to 5-1 in the sixth with Gordon Beckham driving in two runs with a two-out single.
Royals RHP Luke Hochevar, on the disabled list with an elbow strain, threw 25 pitches in batting practice Saturday. He is scheduled to begin a minor league rehab assignment Aug. 28. ... Royals RHP Brian Bannister is scheduled to throw two innings, a 25 pitch-limit, on Monday for Triple-A Omaha. Bannister is on the disabled list with rotator cuff tendinitis. ... RHP Gil Meche, on the disabled list with a shoulder injury, threw a scoreless inning to begin a rehab assignment with Omaha. ... White Sox manager Ozzie Guillen opted against bringing back RHP Edwin Jackson, who threw seven pitches Friday before the game was rained out, to start the second game of the doubleheader. "He wanted to go, but the smartest thing is not to pitch him," Guillen said. "I'd rather lose a game than lose a pitcher. I'm not going to risk a career or a year just cause we want to win a game.