Soriano was 4-for-5 with the three homers in the first four innings and the Cubs continued their strong road play by beating the Atlanta Braves 9-1 on Friday night.
The Cubs have won five of their last six games, including two straight over the Braves.
The Braves have lost six of seven, including four straight in which they have scored a combined seven runs.
Soriano is 13-for-23 (.565) with four homers as the Cubs have won four of five games on their road trip. He hit homers in three straight games last week and has six already in June.
"This is what we were looking for," said Cubs manager Lou Piniella. "He's starting to give it to us.
"I tell you, when he's swinging the bat well, he's certainly fun to watch."
Soriano led off the game with a homer off Lance Cormier's first pitch before adding another first-pitch homer in the second inning.
Soriano's third homer came in the fourth inning, leaving him in excellent position to become the 16th major league player _ and the first Cub _ to hit four homers in a game.
"I was trying to hit it hard and make a good swing and see what happens," said Soriano, who walked, grounded out and singled to left in his final three plate appearances.
Soriano didn't become the first Cubs player to hit four homers in a game, but he called his second career three-homer game "very exciting for me."
"I feel very good, especially after I hit a home run with the first pitch," he said.
Soriano lifted his batting average to .326 with the four hits.
The sight of Soriano crunching a fat fastball to lead off the game made Braves manager Bobby Cox cringe.
"Number one, he's a great hitter," Cox said. "Number two, you have to make good pitches to a good hitter. We didn't even come close to doing that."
In the fifth inning, Braves reliever Oscar Villarreal threw three balls to Soriano before issuing an intentional walk. The walk drew boos from the fans at Turner Field but didn't surprise Cubs pitcher Sean Marshall.
When asked how he'd pitch to Soriano, Marshall said "I would have walked him."
Soriano, facing reliever Blaine Boyer in the seventh, grounded out to shortstop Edgar Renteria. He singled and was thrown out trying to stretch it into a double in the ninth against Chad Paronto.