The striker has penned a three-year deal, with the Tigers retaining the option of a fourth, to become the club's eighth summer signing on deadline day in a £9.5 million deal.
As revealed by Goal on Wednesday, Bruce turned his attention to the Uruguay international as Shane Long's replacement after Blackburn rebuffed the Premier League side's offers for Jordan Rhodes.
"Abel is a fantastic signing and highlights just how far the Club has come in such a short space of time," manager Steve Bruce told the club's official website.
"He is an exciting talent and like myself, I’m sure the supporters can’t wait to see him in action."
Hernandez's arrivals marks the second time the club have broken their transfer record this summer following the £8m deal to make former loanee Jake Livermore's move from Tottenham permanent.