Available on a free transfer following the expiration of his Peterborough contract, he has signed a two-year deal, having helped the Tigers to finish second in the Championship and secure promotion to the top flight.
The versatile Scotland international, who can play on the wing, behind a front man, or in midfield, arrived from Peterborough in February.
The 27-year-old made a great start to life at Hull, scoring four times in five games in March and winning the npower Championship player of the month award.
A wonder show
And, after Boyd had scored twice in his home debut, a 5-2 win over Birmingham, Hull boss Steve Bruce said: "It was a wonder show.
"I've always been a big admirer but I didn't know he was that good. If he can keep performing like that, then we've got some player on our hands."
Boyd did not add to his four-goal tally over the closing weeks of the season, as Hull stumbled over the line somewhat, but still finished the campaign with 11 goals.
Having made over 100 appearances for Stevenage Borough, Boyd joined Peterborough in 2007 and went on to make over 250 appearances for Posh.