The 30-year-old Dutchman spent four-and-a-half years at Goodison Park, amassing 140 first-team appearances and scoring five goals.
However, Heitinga's playing time has been restricted to just five appearances this term and has been allowed by Everton manager Roberto Martinez to join Fulham on a permanent deal.
"I'm really pleased to get the move completed and I'm looking forward to playing my first game," Heitinga told the club's official website, www.fulhamfc.com.
"I think it's a good move for myself and I'm looking forward to meeting my team-mates.
"I've spoken already with Rene Meulensteen and I think it's the right club for me.
"This is a club with a great history and I always enjoyed playing at Craven Cottage, I really like it as a stadium. It's not one of the biggest but it's got something special."
Heitinga moves to west London initially until the end of the season and will hope to impress enough to earn a call-up to the Holland squad for the World Cup.
The defender came through Ajax's fabled academy before moving to Atletico Madrid in Spain and on to the Premier League with Everton.
"Of course I know Maarten Stekelenburg very well - we were players at Ajax together and we played many years in the national team together," Heitinga said of the Fulham goalkeeper.
"I chose Fulham because the feeling was good and what was also important was the conversation between me and Rene.
"He knows exactly what he wants and I know exactly what I want. The main thing is to keep Fulham in the league and hopefully the boys will start with a win against Southampton."