The 27-year-old midfield ace, who leads the competition for goal assists so far this season, was a top contract priority for the club.
 
Phoenix chief executive Tony Pignata said Bertos was the sort of player the club could build a strong team around in the future.
 
"Leo's had a fantastic season for us so far and we believed it was imperative that we re-signed him and that we did it quickly before all the other clubs came chasing him," said Pignata.

"We identified him some time ago as a priority and he was always keen to stay here in Wellington. Leo will continue to be a significant core player around whom we can build an extremely competitive team in the coming seasons.
 
"Leo's the sort of player fans love to watch because he's always involved, he takes opposition players on and he creates chances."
 
The deal with Bertos also signals Phoenix's intent to become a major player in the Hyundai A-League this season and beyond.
 
"This is indicative of the club's commitment and that of (owner) Terry Serepisos that we're here for the long haul," said Pignata. "We need players, fans and sponsors to understand that this club has an extremely bright future in the short, medium and long term.
 
"We'll be around for the years to come and we're currently working with Football Federation Australia to ensure that does happen."
 
Bertos was thrilled to have his playing future secured in Wellington until at least 2012/13.
 
"This is my home town, my family's here and so are my friends. But it's also a great move for me career-wise," said Bertos.

"The club has been excellent from day one and is going from strength to strength. I'm honoured to be given the opportunity to keep playing a part on the field as a Phoenix player and off it as someone who can contribute to the amazing developing the game in New Zealand."
 
Bertos, currently on the Gold Coast preparing for  Phoenix's match against Gold Coast United on Friday night, is also an international player on the cusp of appearing at the World Cup finals with New Zealand.
 
Phoenix's six All Whites (and coach Ricki Herbert) will fly to the Middle East following Friday night's match for the first of home-and-away qualifiers against Bahrain.
 
Bertos added: "That's another great thing about having a professional club here in Wellington. As well as providing more opportunities for Australian players in the growing competition, as an All Whites group it's allowed us to play top-level football together.
 
"I'm not sure we'd have got as close to qualifying for the World Cup as we have without the club in Wellington and I'm looking forward to continuing my career here."