The team will again carry an extra bullpen arm, leaving them with just four players on the bench on Wednesday.
Mets relievers Buddy Carlyle or Dana Eveland is expected to be demoted to make room on the roster for Brown.
Brown is hitting .359 with 13 home runs and 31 RBI in 142 at-bats in Triple-A this season.
He started the season with the Mets, but hit just .185 with a home run and five RBI in the 27 at-bats before being demoted in late April.
9:56: Brown in en route to Chicago, he tweeted: