A review committee established by the Native American Graves Protection and Repatriation Act made the decision on the 20th anniversary of the passage of the act, the Anchorage Daily News reported.
The act created a federal law under which Native peoples can claim human remains and cultural objects held by museums and federally funded agencies.
The Tlingit matter marked the first time a dispute over Alaska Native sacred or cultural objects reached the NAGPRA repatriation review committee, chairwoman Rosita Worl said.
Usually museums and tribes manage to reach some kind of agreement, she said.
Most of the artifacts in dispute were purchased in 1924 by Louis Shotridge, a Tlingit man who worked for the University of Pennsylvania, which added them to its Museum of Archaeology and Anthropology.
Worl, a Tlingit anthropologist and president of the Sealaska Heritage Institute, has said Shotridge was "a better anthropologist than he was a Tlingit."
"He did a great job for the museum in terms of acquiring or taking collections. And I guess he believed he was doing the right thing by preserving it," she said.
"Whereas a good Tlingit wouldn't do that," Worl said. "They would see the most important thing is it's used in our ceremonies and see it as sacred objects. Which they are."
On Nov. 19 in Washington, the NAGPRA repatriation review committee voted unanimously, saying the collection included sacred items and the museum "does not have right of possession" to the objects.
University spokeswoman Lori Doyle said the museum is disappointed with the committee's decision but university officials "hope to continue to work with the claimants to find a resolution."