The Spanish goalkeeper, who also collected the honour in February, garnered 41 per cent of the vote in the latest poll, conducted on ManUtd.com and the club's six foreign-language websites.
Michael Carrick and Shinji Kagawa shared between them almost the same number of votes De Gea won on his own, with Wayne Rooney, Nemanja Vidic and Rio Ferdinand rounding out the five-man poll.
De Gea has now won the award four times since arriving at Old Trafford at the start of the 2011/12 season, more than any other United player during the same period.
In March, De Gea played in all five of the Reds' fixtures, keeping clean sheets in the league against Norwich City, Reading and Sunderland to extend his unbeaten Premier League run to six games. In Europe he performed well against Real Madrid (and was powerless to stop either goal), while last-minute heroics against Chelsea at Old Trafford earned United an FA Cup replay.
Speaking in the latest edition of Inside United, De Gea, who also earned a call-up to the senior Spain squad in March, admits he's thriled with his recent performances.
"I'm satisfied because keeping clean sheets is key for the whole team. not conceding helps us play better - it's a big contribution to our goal.
"I put a great effort into what I do and to know I'm valued by the fans and club gives me much motivation."