The Kings announced the procedures Thursday.
Brown had surgery on his left shoulder, and Lewis had surgery on his right hand. Both two-time Stanley Cup winners are expected to recover well before the start of training camp.
Brown had a resurgent year under new coach John Stevens, scoring a career-high 61 points in his 14th season with the Kings. The former captain hadn't scored more than 36 points in any of the previous five seasons.
Lewis also hit his career high last season with 26 points in his eighth full campaign for Los Angeles.
The Kings were swept by Vegas in the first round of the playoffs.