The Chelsea youngster opened the scoring for the Millers on Saturday but the home side were unable to hold out Cardiff City, eventually succumbing to 2-1 defeat after a late brace from veteran striker Rickie Lambert.
Brown, who scored his first Rotherham goal in a 2-2 draw with Bristol City two weeks ago, was well-placed to fire home a header from Middlesbrough loanee Dael Fry after a long throw-in from Greg Halford failed to be cleared by the Cardiff defence on the hour-mark.
Unfortunately for the home side though, Lambert asserted his experience on the situation and headed home an equaliser before a deflected effort helped the Bluebirds steal the points at the AESSEAL New York Stadium.
The result sees Alan Stubbs' men occupying 23rd position on the tier two table with just one win from nine matches.
Check out the highlights below, courtesy of Rotherham's official YouTube Channel: