"We're going to play him just about every day," manager Don Wakamatsu said. "Obviously we'll look at some matches, and when it's a night [game followed by a day game], we might give him one off and let [Josh] Bard catch in that situation, but he's up here to play."
Moore replaces Rob Johnson on the 25-man roster.
The 26-year-old receiver batted .321 with three home runs and 15 RBIs with Triple-A Tacoma. He started the season with the Mariners, batting .193 with one home run and four RBIs before suffering a knee injury in May.
"I have been ready," Moore said. "I feel healthy and have been working a lot down there on being more consistent. I'm going to bring it up here, stay with my plan and continue to work on it."
Moore said he has a new stance, which includes holding his hands higher.
"I have been working my tail off on my offense," Moore said. "I feel comfortable right now."
He said one of keys to his success is getting to play regularly and not have to worry that if he goes hitless in one game he'll be on the bench for the next game.
"I've already experienced that," Moore said. "I've told myself not to let that happen again. I'm ready to go, and I hope it is my job, and I play every day."
Johnson batted .191 in 61 games for the Mariners. He hit two home runs and drove in 13 runs.