The 25-year-old Ivorian striker becomes Steve Bruce's sixth signing of the summer as the Tigers look to build on the squad that secured promotion from the Championship last year
Sagbo joins on a two-year deal following a three-year spell with Evian.
The 25-year-old Ivorian expressed his delight at joining the Premier League newcomers.
"I am so happy to have signed for Hull City, and I am very grateful for the opportunity," he told the club's official website.
"I can't wait to get going, and I look forward to meeting my new team-mates this weekend.
"I want to show the coaches and the fans what I’m all about, but not just with my physical presence. I also hope that my mobility and technical skills can add to what is already a good footballing team.
"I was delighted when the call came through. I had a very good feeling from the manager, that he really wanted me to come to Hull. That feeling was mutual.
"I am excited to get started in the Premier League. It is a league that I’ve watched closely, and I know all about it. I’m looking forward to the challenge, and I aim to score many goals."
Sagbo becomes manager Steve Bruce's sixth permanent signing of the transfer window, while fellow striker Danny Graham joined on loan from Sunderland earlier this month.