The jury for the latest case had been selected but a deal was done in the early hours of the day the US trial was to begin, according to news site Ars Technica.
Unwired Planet had sought $33m (Â£25.7m) and a cut of iPhone and iPad sales, which it said made use of its tech.
The terms of the settlement have not been made public.
Apple had previously described the case - involving voice recognition and data transmission inventions - as being "frivolous".
Nevada-based Unwired used to develop mobile software, when it was known as Openwave Systems, but no longer makes products of its own.
It acquired the rights to the inventions involved in the case from Ericsson in a controversial deal. Rather than purchase the technologies outright, Unwired instead agreed to share future revenues generated from the patents with the Swedish telecoms equipment-maker.
That has led some to describe Unwired as a "patent troll" - although the firm's legal team described the term as "hackneyed".
"Our ambition is to bring efficiency and fairness to patent licensing and create a marketplace where product manufacturers and innovators feel confident that high quality technology is available at a fair and reasonable price," a spokeswoman for PanOptis Patent Management, which recently bought Unwired's licensing business, told the BBC.
"Over the past nine months since we acquired the Unwired Planet patent portfolio, we have actively resolved a majority of the existing litigation that had been initiated by Unwired Planet, including suits involving Samsung, LG and Apple."
Earlier this month, the firm scored a court victory over Huawei in London.
The Chinese company was ordered to pay a global fee for use of Unwired's 4G patents or face a UK sales ban.
Unwired previously won a case against Samsung involving 2G technologies.
It is also involved in disputes with Google and HTC.
Apple has settled a patent dispute with a litigant that had already beaten Huawei and Samsung in court.