The full commission plans to issue a final decision in the case in October.
Rovi shares fell as low as $24.20 following the news but later recovered to $25.43, down 4.1 percent, in afternoon trading. Netflix shares were up 0.5 percent at $221.37.
In mid-2012, Rovi accused several companies of infringing on its patents for on-screen guides for TV listings. LG Electronics and its subsidiaries settled with Rovi, as did Mitsubishi Electric Corp and its subsidiaries.
Netflix had been accused of infringing on four Rovi patents but was found innocent in all cases.
At the same time, U.S. consumer electronics company Roku, founded in 2008 to stream Netflix videos, was found innocent of infringing on one Rovi patent.
ITC Judge David Shaw declared one of the Rovi patents invalid but said the other three were valid. His decision was dated June 7 but appeared on the ITC web site on Monday.
In a statement, Rovi noted the finding of validity for three patents.
"We are pleased that the majority of the patents involved were confirmed valid," Samir Armaly, a Rovi executive vice president of worldwide intellectual property, said in a statement. "We will continue to seek to license companies to the technologies that we've developed and to protect our intellectual property from unlicensed use."
Netflix said only that it was "pleased with the initial determination and look(s) forward to the full commission confirming it."
The case, at the International Trade Commission, is No. 337-845.
(Reporting by Diane Bartz; editing by Ros Krasny and John Wallace)