Jackson, 31, is the leading points scorer in the Guinness Premiership and helped Saracens qualify for this weekend's semi-final against Gloucester.
"I was very shocked when I heard the news and couldn't quite believe it to be honest," Jackson said after collecting the award at a gala ceremony in London this evening.
"It is a real honour to be voted by your peers. It is the greatest achievement of my rugby career to win this award and a very proud moment.
"My thanks have to go to my team-mates at Saracens for the support I have received this season."
Jackson signed for Saracens from Waikato in November 2004 and has flourished this season under the stewardship of director of rugby Alan Gaffney.
Ward-Smith's achievement in polling second was particularly impressive given he has not played since badly damaging knee ligaments in January.
The New Zealand-born number eight suffered the injury just a week before his proposed England debut in the RBS 6 Nations and is now rated as "borderline" to be fit in time for the World Cup.
Also nominated for the PRA Computacenter players' player award were London Irish centre Mike Catt and Bristol lock Roy Winters, whose reward for an outstanding season was a place in the England squad for the tour of South Africa.
The shortlist for Mercedes Benz Young Player of the Year - the Nick Duncombe Memorial Award - featured five England internationals who all made their debuts this season.
Harlequins winger David Strettle won the prize, beating Wasps flanker Tom Rees into second place with London Irish fly-half Shane Geraghty third.
Completing the list of nominees were Newcastle fly-half Toby Flood and Gloucester centre Anthony Allen.
England's World Cup-winning captain Martin Johnson was inducted into the PRA Barclays Hall of Fame, following the likes of Mike Gibson and David Duckham.
Former England and Harlequins centre Will Greenwood was presented with the PRA Kingston Smith Special Merit Award for his outstanding contribution to rugby.
And former Sale centre Robert Todd was awarded the Towergate Tlc Blyth Spirit Award for his courage in successfully battling against skin cancer.