"It's lonely for me, not that I don't love all my colleagues. I do," Ginsburg said. Women bring a life experience to the court that men can't, she said.
When members of the public visit the court to watch the proceedings, Ginsburg said she can't help but wonder what they think.
"There I am all alone, and it doesn't look right," said Ginsburg, who was appointed to the court by President Bill Clinton in 1993.
The Supreme Court of Canada has four women, including the chief justice, and the United States could benefit by looking at the legal systems of other countries, she said.
Ginsburg, 76, had surgery in February for pancreatic cancer. She has said the operation successfully removed the cancer but didn't address the issue Friday.
Ginsburg has said she wants to match the tenure of Justice Louis Brandeis, who served for more than two decades until age 82.
"It's the best and the hardest job I've ever had," she told students.