Craig Cathcart has completed a move to Championship side Watford.
The Northern Ireland international will officially be unveiled by the Hornets on July 1 when his contract with Blackpool expires.
It will be the second time that Cathcart has turned out for Watford, having spent time on loan at Vicarage Road while on the books of Manchester United in 2009.
The 25-year-old has agreed a two-year deal.