The former Birmingham City man has completed a two year deal after being released by Gary Rowett, the former Brewers boss.
Reilly broke into the first team squad at St. Andrews under Lee Clark, and went on to make 60 appearances in the Championship.
His loan spell at the newly promoted League One side was scuppered last season as he picked up a hamstring injury that ruled him out of the season.
But Jimmy Floyd Hasselbaink has moved to make Reilly a permanent fixture in the Burton squad as they prepare to make their bow in the third tier of English football.
Burton assistant boss David Oldfield said: “He is a valuable addition. He is a good character with good quality and he still has lots of potential.”
Reilly will remain at the Pirelli Stadium until June 2017.
Burton Albion fans….. What do you make of this news? Are you glad to see this ex-Birmingham City man join Hasselbaink’s revolution at Burton? Let us know your thoughts and opinions in the comments below!