The Chile international, who signed for United in 2012, has been on loan with Croatian side Dinamo Zagreb since August.
Having scored 15 goals in all competitions so far, Dinamo have taken the decision to tie the 20-year-old down to a permanent contract.
"We have bought him outright for £775,000. We have already signed a contract with him for the summer. There is no doubt it - the deal is resolved," Dinamo head coach Zoran Mamic told Prensa Football.
Henriquez failed to make single senior appearance for the Red Devils.