The 22-year-old will stay at the Yorkshire club until June 2015, with the Terriers having an option for a further year.
Gobern missed a large chunk the season after undergoing ankle surgery but returned in February to become a virtual ever-resent under new manager Mark Robins.
"I'm delighted Oscar has agreed this new contract for a number of reasons," Robins told the club website.
"On the footballing front, Oscar has performed well during my time at the club but he clearly has potential to improve too. Not only can he contribute on the pitch now, but Oscar can play a big role in our team going forward.
"The club took up the option of a year's extension on Oscar's previous contract, but having a young player like him on a one-year deal wouldn't have been commercially workable for Huddersfield Town - he would have been able to potentially speak to other clubs again within six months.
"We had to secure Oscar on a longer contract and I am delighted this has been done."
Meanwhile, striker Lee Novak will leave Huddersfield at the end of his contract this summer after rejecting a new deal.