Bullard, who broke into Fabio Capello's England squad this season, joined for a fee of 5 million pounds ($6.89 million), the northern club said on their website.
Hull have suffered a dip in form over the last two months after making a superb start to their first campaign in England's top division and manager Phil Brown said Bullard would help steady the ship.
"We're trying to improve a squad that has been competing in the Premier League and that just needed a bit of bolstering," Brown said. "Jimmy is a good player, end of story."
Bullard, well-known for his industrious midfield play and his delivery from set pieces, was called up by Capello in August but is yet to win an international cap.
He joined Fulham in 2006 from Wigan Athletic but suffered a career-threatening knee injury weeks later and only returned to first-team action last January, playing a major role in keeping Fulham in the top flight.
Meanwhile, Guinea defender Kamil Zayatte has signed a permanent contract with Hull City after originally joining on a loan deal from Swiss club Young Boys.
"I think he has come into the Premier League and surprised everybody in the last six months," Hull manager Phil Brown told the club's website.
Zayatte's contract runs to 2012.
