Former Liverpool man Ince had previously been at Blackpool but spent the second half of last season on loan in the Premier League with Crystal Palace.
With 22-year-old Ince out of contract at Bloomfield Road, he had been linked with a move to Serie A club Inter - where his father Paul played for two years.
However, he has now moved to the KC Stadium on a two-year contract - following Robert Snodgrass and Jake Livermore to the club - with Hull also confirming negotiations over a fee will continue due to the player's age.
"Due to the player’s age, negotiations between the Tigers and Ince's former club Blackpool over a compensation fee continue," they stated on their official website.
"Should the two clubs fail to come to an agreement, the fee will be determined by a tribunal."
Ince, a former England under-21 international, originally caught the eye with his performances in the 2012-13 campaign where he scored 18 goals in the second tier before adding a further seven in the first half of the 2013-14 campaign.
That encouraged Palace manager Tony Pulis to sign him on loan, although he scored just once in eight starts at Selhurst Park.
