The American international sealed a £6m move to the Black Cats earlier this week after spending two seasons with AZ Alkmaar in the Eredivisie.
"It was really important for me because I had no experience in European football anywhere, so going on loan to Hull was good for me in terms of just getting my feet wet and to start playing," Altidore told the club's official website.
"It was a good experience for me – I learned a lot about myself. I look back on it as one of the things that helped shape me into the player that I am today."
Altidore scored just one goal for the Tigers in 28 appearances in the 2009-10 season.