The win put the Antlers four points clear on top of the table with a game in hand and stretched their winning streak to five in a row.
Koji Nakata struck the only goal of the match in the 16th minute to ensure Oswaldo Oliveira’s side took home all three points.
“I'm very satisfied with the result,” Oliveira said.
“I had expected it to be a tough game, because Gamba Osaka are a wonderful team which have the top players in Japan.
"We had several chances at the beginning and we took one of them. One thing I was disappointed with was that we couldn't add another goal. But it is wonderful that we defeated Osaka during such a tough period of time."