Brewers manager Ron Roenicke made the announcement after Friday's 10-5 exhibition loss to Seattle.
Milwaukee opens at home April 6 against Colorado.
Lohse went 13-9 with a 3.54 ERA in 31 starts for the Brewers last season. He struck out 141, two off his season high.
"I talked to Kyle the other day," Roenicke said. "He knew what we wanted him to do, but I just wanted to say something to him. Just his experience, the type of quality pitcher he's been for a few years. Upstairs, he's a solid guy."