McCarthy won the Queensland Cup and State Championship when he was with the Northern Pride in 2014. The Cutters are the feeder team for NRL side St George Illawarra.
The forward said the Cutters are well placed to take out the competition.
“I am really excited to be playing in the finals series its now the business end of the year, meaning a lot of hard work still needs to be done,” McCarthy told the Dragons website.
“I know it sounds cliche and obvious, but the result is the most important thing this time of year.
“We’ve showed how strong our squad is in recent weeks and everyone in this team has each other’s back.
“There is a real camaraderie within the playing group and I know we will take a lot of confidence out of finishing second in the competition and first overall in defence.
“We’ll go in well prepared for this game and I am confident whoever runs out onto the pitch on Saturday will do a great job.”