The Australian joined from Championship club Featherstone Rovers in December initially on a 12-month deal.
However, he has scored five tries in just six games so far, including a hat-trick in his last outing against Huddersfield Giants.
Hitchcox is set to return from a hand injury in the match at Warrington tomorrow night and the former Gold Coast Titans player admitted: “I’m really excited.
“It’s obviously a great club and I’m growing to love it here in Cas.
“Everyone has been really welcoming to me and I’ve made some good mates since I arrived.
“There’s a real good vibe throughout the club, all the way from the staff, the young players to the first-team players, so I’m really liking it.
“I love playing here; it’s the most vocal crowd that I’ve been part of, they are really something.”
Castleford coach Daryl Powell has been impressed by the 26-year-old’s dedication.
“Jy Hitchcox has shown so far what a good quality player he can be in Super League,” he said.
“His speed and footwork have caused plenty of trouble to defences and I’m confident he will continue to improve within our environment.
“I am delighted he has agreed a two year extension and I look forward to working with him during that time.”