Howard led the league this season with 789 defensive rebounds and averaged 14.1 rebounds, 2.4 blocks and 1.4 steals in 78 games with the Magic.
"I could have just stopped after winning one award, but I want our team to be successful and I know it starts with me and it starts on the defensive end," Howard said.
"Me playing defense is about helping my team win. And I think that shows every night when I'm out there trying to be there for my team and erasing the defensive mistakes."
Howard, the first overall pick in the 2004 NBA Draft, was third in offensive rebounds (309), second in total rebounds (1,098) and third in blocks (186) in the regular season.
Howard received 114 first-place votes from a panel of 120 sports writers and broadcasters throughout North America that voted on the award.
Dikembe Mutombo and Ben Wallace are the only other players to have won the award more times. They each won it four times.
(Reporting by Frank Pingue in Toronto; Editing by Julian Linden)