The midfielder, who saw a January move to Nottingham Forest collapse in controversial circumstances when he failed an eye test, has opted to swap a relegation scrap for a chance of promotion on Humberside.
And crowd favourite Boyd, who scored 75 goals in 297 appearances, has made a point of telling Peterborough supporters the decision was his alone.
He said: "The chairman Darragh MacAnthony and I spoke at length and he informed me he had turned down five bids from Hull City and three other bids from three other Championship sides because it was not about the money.
"He was desperate to keep me at the football club so that Peterborough United had a better chance of retaining their Championship status.
"However, I explained that the opportunity to join a club like Hull City at this stage of my career was too good to turn down.
"After a long and emotional telephone conversation, he and the manager, reluctantly agreed to let me go and try and fulfil my dream.
"My message to the supporters is simple. Thank you very much for all your support over the time I have been with Peterborough. You have been magnificent."