The 22-year-old has long been expected to link up with the Black and Whites in 2014, and Pearson confirmed the rumour on Monday.
In an address to the club's fans ahead of the Super League play-off eliminator against Catalan Dragons on Friday, the former Hull City chief executive has laid out his plans for the transfer market, with Thompson's arrival amongst them.
"We have already signed Jacob Miller for the 2014 season and added Mickey Paea, a stand-out Super League player for next season," Pearson said.
"We are also pleased to announce Jordan Thompson from Castleford, who although only 22 has played close to 100 Super League games and was much coveted by other top Super League clubs."
Pearson now plans to add two forwards and another outside back to Peter Gentle's squad, but is prepared to wait until the end of the World Cup to make decisions.
"Our plan is to bring three more players in, an outside back, front-rower and probably a back-rower as well," he added.
"We will keep our powder dry on the forwards until the World Cup as we feel to have no quota or cap space available when so much new talent will be on show would be a mistake."
Hull reached the Challenge Cup final this season - losing to Wigan - and have made the play-offs with a sixth-placed finish.
Reports earlier in the season suggested coach Gentle would be sacked despite that - a story which was denied at the time - and although Pearson did not return to those rumours on Monday, he spoke of the progress made under his and Gentle's two-year tenure so far.
"I feel we are making strong progress as a club. We are pursuing strongly the ethos of a Club Hull with talented young players being given a chance to represent their city," he added.
"We feel very strongly that this is the way forward in order to once and for all establish Hull FC as a Super League power."
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- Super League
- Jordan Thompson
- Hull City
- Catalan Dragons