Although Apple is a US company, iPhones are assembled overseas and shipped to the US and other countries.
The ruling will not enter into force until the entire ITC panel and President Donald Trump review McNamara's decision.
In a case decided on Tuesday, the ITC ruled for Apple in a case dating back to 2017.
"We are pleased ITC has determined that Qualcomm's latest claims have been invalidated," Apple spokesman said in a statement. "This is another important step to ensure that American companies can compete fairly on the market."
Qualcomm was immediately available to comment on the ITC judgments.
In this long-standing feud, both companies were temporarily at the top.
But in 2017, Apple was released suing Qualcomm for $ 1 billion after the chip maker ceased to pay for the exclusive right to use its chips in iPhones.
Qualcomm refused to pay after the European Union started the investigation. The EU eventually considered the payments illegal, and in January 2018, the European Commission ordered that Qualcomm pay a fine of $ 1.2 billion for the matter.
Apple's share fell 1% on Tuesday. Qualcomm's share rose more than 2%.
– Julia Horowitz of CNN Business contributed to this report.