Barnsley will be the first opposition to play at the New York Stadium in Rotherham's opening pre-season friendly at their new home.
The Millers will take on Keith Hill's Championship side on Saturday, July 21, followed by the visit of another local rival, Doncaster, who will be the second team to visit the New York Stadium three days later (July 24).
Rotherham stadium manager Paul Davis told the club's official website: "We're delighted to be welcoming Barnsley and Doncaster to the New York Stadium.
"Both sides will be preparing for the upcoming campaign after just completing tough seasons in the Championship, and unlike in previous years they will provide a test to the stadium as well as the team on the field.
"We are sure that both sides will fill their quota of away support, reflecting the enormous interest in the stadium."