Soriano, who has been mired in a slump, hit his 54th leadoff homer Tuesday night in the Cubs's 6-5 loss to the Braves in 12 innings at Turner Field.
The only player in Major League history who has more is Henderson, who did it 81 times.
Soriano, who was tied with Craig Biggio for second place, connected on the fifth pitch from Atlanta starter Kenshin Kawakami. Of the left fielder's 13 home runs this season, five have come leading off.
The homer was Soriano's only hit in six at-bats, however, as his average dropped to .244. He batted just .216 in May and finished the month in a 6-for-45 slump. His previous homer was May 17.
Soriano has a sore left knee, but he doesn't want to come out of the lineup.
"I don't think we'd even be talking about it if he was going better," manager Lou Piniella said before the game.
Soriano, who has played in 48 of 50 games, said that he has been favoring the knee a little at the plate, demonstrating his stride into the ball. But he feels the soreness mostly when stopping on the bases or in the field.
"That's when it hurts," Soriano said.
Soriano has gone through plenty of slumps before, including home run droughts.
"That's going to happen to me," he said. "Then I get my hitting back, and I become very dangerous. I will get my home runs."
Especially leading off a game. That has become Soriano's specialty in good times and bad.
Guy Curtright is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.