Prince Edward, the Queen's cousin, was given a guided tour of the Millers' new home by honorary ambassador Howard Webb and chairman Tony Stewart before he unveiled a commemorative plaque.
Stewart, who funded much of the £20million project himself, revelled in the royal's visit.
"Rotherham United Football Club were visited by the Duke of Kent who looked and listened whilst being shown around the stadium by a host of people connected with the events here.
"He showed a great interest as he was told about the activities that take place here in the heart of Rotherham, and over the time he was here, he got the message that this is more than a football stadium.
"This is a venue to benefit all the areas of Rotherham, young and old, this is a stadium for the people."
The Millers moved into the 12,000-seater stadium in the summer after spending four years at Sheffield's doomed Don Valley Stadium following their move from Millmoor.