Smoltz (1-2) allowed two runs in six 2-3 strong innings as he continued along the recovery road from the ligament transplant surgery that saw him miss the whole of 2000.
Mark McGwire homered in his first game since 15 April, leading St Louis Cardinals to a 6-2 win over the Milwaukee Brewers.
McGwire, activated from the Disabled List before the game, connected with Paul Rigdon to launch his 556th career home run, and just his second this season.
The home run champion has missed one and a half months after a setback in his recovery from close season surgery for tendonitis in his right knee.
After his home run put the Cards 2-0 ahead, McGwire said: "It's just nice to have good at-bats. A home run is a home run."
McGwire's return eclipsed the efforts of rookie Albert Pujols who homered twice as the Cardinals won for the 15th time in 20 games.
Pat Meares slammed a tie-breaking three-run homer in the seventh inning, off Dan Miceli (0-5) whose harsh criticism of Boles hastened Florida's decision to sack the manager.
Paul Lo Duca went 6-for-6 at Dodger Stadium and scored the winning run on Shawn Green's 11th-inning single off Ron Villone (0-2) to squeeze Los Angeles Dodgers past the Colorado Rockies 11-10.
Todd Helton hit his first major league grand slam and tied his career best with five RBIs.
Pat Burrell hit a two-run homer in the 10th inning off Armando Benitez (3-2) to clinch a 5-3 win for Philadelphia Phillies over New York Mets.
Chicago Cubs won its eighth successive game with a 9-6 win over Cincinnati Reds in 13 innings.
It wasn't unlucky for Ricky Gutierrez who homered in the 13th inning, after Eric Young had singled home the tie-breaking run off Scott Winchester (0-1).
Mark Grace extended his hitting streak to ten games and took a solo home run off Tim Worrell (1-1) to lead Arizona Diamondbacks to their fourth straight win at San Francisco Giants
John Smoltz claimed his first win for Atlanta Braves since October 1 1999 in a rain-shortened win over Montreal Expos.
Smoltz (1-2) allowed two runs in six 2-3 strong innings as he continued along the recovery road from the ligament transplant surgery that saw him miss the whole of 2000.
National League
Paul O'Neill hit the winning run as New York Yankees notched their fourth successive win over Boston Red Sox.
O'Neill struck a solo homer and doubled as well as making the winning hit to ruin former Yankee pitcher Dave Cone's Bo-Sox home debut.
Mariano Rivera got his 15th save in 16 chances to keep the Bronx Bombers one and a half games ahead of Boston in the NL East.
Paul Abbott (3-2) pitched a six-hitter for his first career complete game and John Olerud went 4-for-5 as Seattle Mariners completed a four-game sweep at Kansas City Royals. Seattle has won five straight and own baseball's best record at 37-12.
Dean Palmer homered and drove in a season-high five runs and Wendell Magee also hit a three-run homer as Detroit Tigers halted a five-game losing streak against Cleveland Indians, who have lost three straight.
Jon Garland (2-2) stepped in for injured David Wells and allowed one run and four hits in 6 2-3 innings as Chicago White Sox won its fifth straight following an eight-game losing streak, beating Toronto Blue Jays.
Jose Valentin and Magglio Ordonez hit two-run homers for Chicago.
Gabe Kapler's two-run single broke a 2-2 tie in the eighth as visiting Texas Rangers ended Baltimore Orioles' five-game winning streak.
Frank Catalanotto and Andres Galarraga hit successive solo homers for the Rangers.
Troy Glaus homered and Scott Schoeneweis (4-3) overcame a shaky start as Anaheim Angels added to Tampa Bay Devil Rays' miserable season.
Anaheim added two more runs in the seventh on Adam Kennedy's sacrifice fly and Jorge Fabregas' RBI single off Rusty Meacham (1-3).
National League
Philadelphia 5-3 NY Mets (10 innings)
Chicago Cubs 9-6 Cincinnati (13 innings)
St Louis 6-2 Milwaukee
Arizon 2-1 San Francisco (12 innings)
Los Angeles 11-10 Colorado (11 innings)
Pittsburgh 8-5 Florida
Atlanta 5-3 Montreal (8 innings)
American League
Detroit 12-6 Cleveland
Texas 6-3 Baltimore
Seattle 13-3 Kansas City
Anaheim 3-1 Tampa Bay
NY Yankees 4-3 Boston
Chi White Sox 6-3 Toronto