Quinn, younger brother of Alan has just recently returned to Bramall Lane after a successful loan spell at Danny Wilson's Milton Keynes Dons and has now joined the Millers on a months loan.
Neil Warnock told sufc.co.uk: "I must have had six clubs enquiring about taking him on loan but I've insisted he goes to Rotherham. I'm sure, having picked up experience with the Dons, his enthusiasm and energy will be a help to The Millers."
Stephen Quinn, 19 joins fellow Blades team mate Jonathan Forte on loan at Millmoor and aims to make his debut this Saturday at home to Nottingham Forest.