The Reds agreed an undisclosed fee with Birmingham today for the highly-rated goalkeeper, who joined the Reds initially on loan, and signs a three-year deal.
The 20-year-old enjoyed an impressive debut at Scunthorpe United in the League Cup to help secure the Reds' tie with Everton at Oakwell.
"I'm delighted to get the deal done," Nick told barnsleyfc.co.uk. "Since day one I've really enjoyed training and everything about being here. All the lads made me feel welcome and it's just the right idea to join permanently.
"There's great competition between me and Adam and we'll be fighting it out which will make both of us better."
