"I'll be ready for next year," he said before the team's game with the Houston Astros. "It's six to nine months."
He made the decision to have surgery after receiving a second opinion from specialist Lewis Yocum, who confirmed the diagnosis of the team physician.
Narveson's last start was April 15 at Atlanta, and he was placed on the 15-day disabled list five days later, retroactive to April 16.
"You know it's going to be strong, and as long as it heals right and it doesn't re-tear during the rehab process, you should be good," Narveson said. "(Yocum) was very optimistic."
Narveson has been the team's fifth starter the past two seasons and was 1-1 with a 7.00 ERA in two games this year. In 2011, he finished 11-8 with a 4.45 ERA in 28 starts and is 26-18 with a 4.67 ERA in five Major League seasons.
Narveson said he was told he could try to rehabilitate the shoulder, but there was a risk of a further tear. He said he preferred surgery "and be 100 percent than to flip a coin."
"It's all about your outlook," Narveson said. "You have to be positive. You know it's going to be long, you know it's going to be grueling. You know there's going to be days where it aches and it hurts. But a lot of times the reward comes later on when you get back on the mound."
Righty Marco Estrada has replaced Narveson in the rotation and started Saturday against the Rockies, striking out nine and giving up two hits in five innings but didn't get a decision.
The Brewers also announced the reinstatement of right-handed reliever Kameron Loe from the bereavement list on Tuesday. Loe was placed on the list Saturday after the death of his grandfather. Righty Wily Peralta, the team's top pitching prospect, was optioned to Triple-A Nashville Monday night.