Brayford, 28 has played in all of the Blades League One fixtures so far this season but became the latest player to leave Bramall Lane, following the departure of Che Adams to Birmingham City, the defender has joined the Pirelli Stadium club in a season's long loan deal.
Burton boss Nigel Clough told burtonalbionfc.co.uk: "When we heard John was available it was a no-brainer to sign him. He can cover us anywhere along the back three and the wing-back positions as well so that's the main reason we've brought him in and he's a good experienced Championship player."
Brayford added: "It's been 10 years since I played here but they've still got the foundations of a great club and it's nice to be back. The rise has been incredible and I don't think there's been another team that has done something on the same level."