The Cubs selected Miller's contract from Triple-A Iowa on Monday, Taylor McGregor of Marquee Sports Network reports.
Miller inked a minor-league deal with the Cubs in early February and has spent the entire season in Triple-A, where he has a strong slash line of .299/.352/.459 with 10 steals (in 16 attempts), seven home runs and 57 RBI across 403 plate appearances. He figures to serve in a utility role in the Cubs' infield in the absence of Dansby Swanson (oblique), the latter of whom was placed on the 15-day injured list Monday.