Aluko, 23, has signed a two-year contract after passing a medical at the KC Stadium on Saturday.
"Sone is someone I've always kept an eye on," Tigers manager Steve Bruce told the Hull Daily Mail.
"I had him as a kid at Birmingham when he was considered to be the next superstar. I can remember taking him on tour at 16.
"It took him a while to develop. Some players mature quickly and others take their time to settle into senior football.
"But he's worked hard on his game and he's really come on in Scotland in the last couple of years. He really shot to prominence last year, he took it by storm."
Hull, who began talks with Aluko on Tuesday, are hoping not to become embroiled in legal complications as the Scottish Football Association refuse to issue registrations for players unwilling to transfer contracts to a newco Rangers.
Aluko began his career at Birmingham and joined Aberdeen in 2008 before moving on to Rangers on a free transfer in November 2011.