Soriano proved with three homers in his first three at-bats Friday night that the early-season power slump is history.
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's only other three-homer game also came against the Braves on April 21, 2006, while playing for the Nationals in Washington.
The three homers gave Soriano 10 for the season.
Marshall (2-2) gave up only four hits and one run in six innings in his second win over the Braves in six days.
Marshall walked two batters and had four strikeouts. He also beat the Braves 9-1 Sunday in Chicago, when he gave up six hits and one run in 6 2/3 innings.
It was the second straight strong start against Atlanta by a Cubs' left-hander. Rich Hill gave up three hits in eight innings in Thursday night's 2-1 win over the Braves.
The Cubs improved to 16-15 in road games, including 4-1 on their current road trip.
Cormier (0-2) gave up five runs in 3 2/3 innings.
Cormier, who allowed nine baserunners and three runs in the first two innings, gave up five hits and walked six batters. He walked Mark DeRosa with the bases loaded in the first to force in the Cubs' second run.
In two starts against the Cubs, Cormier has given up 14 hits and 13 runs in 7 2/3 innings. Those are Cormier's only two games since coming off the disabled list.
"Cormier was just a little bit here, a little bit there," Cox said.
"The stuff's there. It's there. It's just, he's rusty."
Michael Barrett hit a homer to left in the fourth to knock Cormier out of the game.
Cesar Izturis led off the fifth with a double off Villarreal and scored from third on Felix Pie's fly ball to left.
The Cubs added two runs off Boyer in the seventh. Felix Pie's single to center drove in Izturis. A throwing error by first baseman Scott Thorman on Derrek Lee's infield hit allowed Pie to score from second.
Pie went 2-for-4 with three RBI.
The Braves, held to only three hits in a 2-1 loss to the Cubs on Thursday night, struggled again. Their only run off Marshall came in the third when Kelly Johnson hit a triple down the right-field line and scored on Yunel Escobar's infield hit.
- Braves C Brian McCann was given another day off after having a cortisone shot in his sore right ankle Wednesday but is expected to start Saturday. Jarrod Saltalamacchia started for the third time in five games.
- OF Cliff Floyd was placed on the bereavement list as he returned to Chicago to be with his sick father. IF Mike Fontenot will be recalled from Triple-A Iowa on Saturday.