Sio, 22, joined Wildcats from Mackay Cutters in June, 2015 on a deal lasting until the end of the current campaign.
The loose-forward played 11 times last term and is every-present so far this year, having featured in all Wildcats’ 13 games of 2015.
“I am excited I get to play at Belle Vue for another two years and be around pretty much the same group of players as what we have this year and build on what we have at the moment,” Sio said.
“I have enjoyed working under [coach] Chris Chester. He has come in and put some structures in place and a lot of the boys are buying into it. It is reflective of our performance on the field.
“I am excited I am part of his plan for the next two years and I have the security that I will be a professional rugby player in the Super League for the next couple of years.”
Chester said: “Mikey gives us plenty of energy both on and off the field.
“He is an important part of our squad so I am pleased we have got something sorted quickly. I am looking forward to working with him over the next couple of years.”