With the score tied at 3 in the bottom of the 10th, Padres first baseman Nate Colbert pinch-hit for pitcher Tug McGraw and drew a leadoff walk from Dave McNally of the Baltimore Orioles.
Colbert advanced to second on a sacrifice bunt by Giants shortstop Chris Speier and scored the winning run on a walk-off single to right-center by Cincinnati second baseman Joe Morgan.
The game was the seventh extra-inning game in All-Star Game history. And the National League had won all seven.
It was also the National League's ninth win in 10 years, giving the National League a 24-18-1 lead in the series.
The lead had changed hands three times before the National League tied the game in the bottom of the ninth to force the extra inning.
The American League took a 1-0 lead in the top of the third.
Detroit catcher Bill Freehan drew a lead-off walk from the Pirates Steve Blass. Freehan advanced to second on a sacrifice bunt and scored on a one-out single to center by Minnesota second baseman Rod Carew.
The National League took a 2-1 lead against Gaylord Perry of the Cleveland Indians in the bottom of the sixth. Hank Aaron of the Braves followed a two-out single by Astros center fielder Cesar Cedeno with a two-run homer to left center -- driving his hometown crowd of 53,107 at Atlanta-Fulton County Stadium into a frenzy.
The American League regained the lead with two runs in the top of the eighth off Bill Stoneman of the Montreal Expos. Boston catcher Bill Fisk singled and scored on a two-run homer by second baseman Cookie Rojas of the Kansas City Royals.
The National League tied the game in the bottom of the ninth against knuckleballer Wilbur Wood of the Chicago White Sox.
Left fielder Billy Williams of the Cubs and catcher Manny Sanguillen of the Pirates opened the inning with back-to-back singles to put runners at the corners. Williams scored when Houston first baseman Lee May grounded into a forceout.
Enter Colbert, who was making his first of three straight All-Star Game appearances. The Padres had two representatives in the game as National League manager Danny Murtaugh of the Pirates invited Padres manager Preston Gomez to be a coach.
Oakland outfielder Reggie Jackson was the only player in the game with two hits.
American League starter Jim Palmer of the Baltimore Orioles allowed a hit and a walk with two strikeouts in three innings. Detroit's Mickey Lolich followed with two scoreless innings, allowing a hit with a strikeout.
St. Louis ace Bob Gibson started for the National League and allowed a hit in two scoreless innings. Don Sutton of the Dodgers allowed a hit with two strikeouts in two scoreless innings and Steve Carlton of the Phillies pitched a scored sixth.
The New York Mets' McGraw struck out four while allowing a hit over two scoreless innings to get the win.