The 2nd U.S. Circuit Court of Appeals in Manhattan said the Communications Decency Act ("CDA"), a 1996 law regulating internet content, shielded Facebook from civil liability.
It also declined to consider the plaintiffs' foreign law claims, noting that most plaintiffs, including relatives and estates of victims, said they were Americans living in Israel.
The plaintiffs originally sought $3 billion in damages from Facebook, for allowing Hamas to use its platform to encourage terrorist attacks in Israel, celebrate successful attacks, and generally support violence toward that country.
Their complaint described Hamas attacks against five Americans, four of whom died, in Israel from 2014 to 2016.
Lawyers for the plaintiffs did not immediately respond to requests for comment. Facebook, based in Menlo Park, California, did not immediately respond to similar requests.
Wednesday's decision is a fresh setback to efforts to hold companies such as Facebook and Twitter Inc liable for failing to better police users' online speech.
It upheld a May 2017 dismissal by U.S. District Judge Nicholas Garaufis in Brooklyn.
In seeking to overturn that dismissal, the plaintiffs said Facebook functioned as a matchmaker between Hamas and people receptive to its messages, and should not be immune from liability as a mere "publisher" of Hamas' content.
Circuit Judge Christopher Droney, however, said it would turn the CDA "upside down" to suggest that Facebook's having become an "especially adept" publisher exposed it to liability.
He also refused to hold Facebook liable because its "friend" and content-based algorithms might have helped direct people interested in Hamas.
"Merely arranging and displaying others’ content to users of Facebook through such algorithms - even if the content is not actively sought by those users - is not enough to hold Facebook responsible as the 'developer' or 'creator' of that content," Droney wrote.
Chief Judge Robert Katzmann, part of the three-judge appeals court panel, dissented from the algorithms discussion.
He said Congress did not consider how broadly to immunize social media companies, when it passed the CDA to regulate online pornography, and might rethink how to treat those accused of encouraging terrorism, propaganda and extremism.
"Over the past two decades the Internet has outgrown its swaddling clothes," Katzmann wrote. "It is fair to ask whether the rules that governed its infancy should still oversee its adulthood."
The U.S. Department of State has designated Hamas a foreign terrorist organization since 1997.
The case is Force et al v. Facebook Inc et al, 2nd U.S. Circuit Court of Appeals, No. 18-397.