ZeniMax, whose empire includes Bethesda Softworks and id Software, filed suit in federal court in Texas accusing Oculus of misappropriating trade secrets relating to virtual reality and infringing on copyrights.
"Intellectual property forms the foundation of our business," ZeniMax chief executive Robert Altman said in a release.
"We cannot ignore the unlawful exploitation of intellectual property that we develop and own, nor will we allow misappropriation and infringement to go unaddressed."
The lawsuit charges exploitation of intellectual property, computer code, and "technical know-how" relating to virtual reality technology that was developed by ZeniMax and shared under terms of a non-disclosure agreement.
"The lawsuit filed by ZeniMax has no merit whatsoever," Oculus said in an email reply to an AFP inquiry.
"As we have previously said, ZeniMax did not contribute to any Oculus technology."
Oculus vowed a vigorous defense against the lawsuit.
Efforts to resolve the dispute have failed, according to ZeniMax.
Facebook in March announced a $2 billion deal to buy Oculus, a startup behind virtual reality headgear that promises to let people truly dive into their friends' lives.
Facebook declined to comment on the litigation, referring inquiries to Oculus.
Facebook co-founder and chief Mark Zuckerberg said that the acquisition of Oculus was a long-term bet that making the social network's offerings more immersive would pay off.
Zuckerberg billed the acquisition as part of a drive to build the "next major computing platform that will come after mobile."
Facebook called Oculus, launched in 2012, the leader in immersive virtual reality technology with a strong following among developers.
The company has already garnered more than 75,000 orders for the $350 Oculus Rift headset development kits.
Facebook said Oculus will maintain its headquarters in Irvine, California, and continue developing the Rift platform.