Fielder hit .337 in 27 June games, leading all of baseball with 27 RBIs, while tying for the lead in home runs (10). His .491 on-base percentage and 25 walks were tops among National Leaguers, while his .747 slugging percentage and 19 runs scored both ranked third.
This is Fielder's second career monthly award, also also having taken home the honor in May 2007.
During the week of June 6-12, Fielder was named the NL Player of the Week after hitting .500 (10-for-20) and leading the Majors with six homers.
The slugger's month was highlighted by a 2-for-3 performance on July 12 that included a go-ahead 440-foot blast in the sixth inning to help the Brewers sweep the Cardinals.
He also had two four-RBI performances (June 6 against the Marlins and June 8 against the Mets) and seven multi-hit games in the month.
Fielder leads the NL with 69 RBIs this season and is also in third place with 21 home runs.