The 28-year-old Australia midfielder, who has scored three times this season, pipped 30-goal top scorer Glenn Murray to the award.
Jedinak told the club website: "It's been a really tough season, I can say that safely. A rollercoaster, but one that I've thoroughly enjoyed.
"To be recognised in this way is a huge honour."
Jedinak will lead out the Eagles against Brighton on Friday night in the first leg of their play-off semi-final.
Boss Ian Holloway added: "It's hard to put into words what this man brings to our club. Have I seen anyone like him in my time? No.
"I totally believe he will lead us, with the other lads, to an unbelievable end to this season.
"We are desperate to give these fans a place at Wembley and to win there."