Phelps, 24, joined the club as a short-term signing from NRL side Canterbury in 2008 but will now remain at the JJB Stadium until the end of 2010.
The Australian said: “I am pleased to be staying with Wigan for 2010 and hope to stay longer by showing even more improvement in my game. I enjoy Wigan and can now look forward to playing my part in bringing some trophies to the Club over the next 16 months.”
Coley, 31, signed from Salford following the Reds’ relegation from Super League in 2007.
He said: “I am thrilled to have agreed and signed a new deal with the Wigan club. The last two years have been great for me since making the move from Salford and I am really enjoying my rugby at the moment.”
Chairman Ian Lenegan said: “Cameron was originally a short-term signing but this year has improved his game significantly and has made the full-back position his own during the past few months. His obvious commitment to Wigan and to his own improvement together with his utility value has earned him the opportunity to have at least one more season with the Club.
“Prop forwards are difficult to find and Andy Coley’s step-up in performance over the past 4 months has earned him a further season with us. He is committed to performing next year as he has done this year and will also be involved in helping the development of some of our young forwards.”
Head Coach Brian Noble said: “Both players have played a big part for us this season and it is good news for the Club that they have signed for 2010.”