The Warriors apparently offered the 32-year-old a chance to remain in the NRL, with a two-year contract offer tabled.
But Pritchard turned down the offer, as he was committed to Hull.
“Frank has shown the type of character he has because I’m sure he could have found a way of not coming,” Pearson told the Hull Daily Mail.
“He’s genuinely excited at coming and being a part of what Lee Radford is building and we are excited about his arrival, because he’s a real marquee player for us.
“We are expecting big things from him on and off the field, because we want him to provide that leadership and set the bar for all our young players too.”