McCain did not discuss the issue during a 45-minute meeting with French President Nicolas Sarkozy, but told reporters later the subject was "one of the first things I would talk about if I were president of the United States today."
China's crackdown "is not correct," McCain said in the courtyard of the French presidential Elysee Palace.
"The people there are being subjected to mistreatment that is not acceptable with the conduct of a world power, which China is," McCain said in response to a question by a Chinese television journalist.
"There must be respect for human rights, and I would hope that the Chinese are actively seeking a peaceful resolution to this situation that exists which harms not only the human rights of the people there but also the image of China in the world."
The White House has urged Beijing to respect Tibetan culture and multi-ethnicity in its society.
McCain was in Paris for a matter of hours at the end of a weeklong tour of the Middle East and Europe. He was traveling as part of a U.S. congressional delegation - including Sens. Joe Lieberman, I-Conn., and Lindsey Graham, R-S.C. - that visited Iraq, Jordan, Israel and London.
The delegation discussed a range of issues with Sarkozy, from climate warming and nuclear energy to the Middle East crisis, Iraq and Afghanistan, where France has troops.
McCain praised the state of U.S. relations with France, crediting Sarkozy, who was elected in May, with the high level of ties after years of tension that followed Paris' lead role in opposing the U.S.-led invasion of Iraq five years ago.
"I think our relations with France will improve no matter who is the president of the United States," he said, "because this president (Sarkozy) is committed to greater cooperation and values our friendship."
A reporter asked if McCain's trip abroad was not a "taxpayer rip-off," used for personal politicking, forcing the Arizona senator to defend the trip. He said he was proud.
Travels to Iraq or Israel and meetings in Europe concern issues that "lay clearly under the jurisdiction of the Senate Armed Services Committee," McCain said.
"Very frankly, I wish every senator ... would take the same trip that we have taken. They would be better informed and they would be better able to make decisions as to how we can defend the national interests of the United States of America in these times of great challenge," he said.
The McCain campaign said Thursday it would reimburse the federal government about $3,000 for political travel expenses incurred during the trip.
On Thursday, McCain attended a $1,000-per-person fundraising lunch at London's Spencer House.
Under terms reviewed by the Federal Election Commission and the Senate ethics committee, McCain will reimburse the federal government $3,000 for a one-night stay at a London hotel and first-class airfare from Washington to London because of the political nature of the event there. McCain had already agreed to pay more than $2,000 for the flight home.
McCain expressed special thanks to Sarkozy and the "the brave citizens of this country" for their troop contribution to Afghanistan where France has some 1,500 soldiers as part of the NATO mission there and another 400 in the U.S.-led operation battling the Taliban and al Qaeda.
McCain reiterated his commitment to the Israeli-Palestinian peace process, saying "we must make progress, we can make progress" and adding that he believes any participation of France and other countries can contribute to peace. The role of France in pressing Iran over its disputed nuclear program has been important, he said.
France pressed for the recent third round of sanctions passed by the U.N. Security Council on Iran for failing to end its disputed nuclear program and assuage fears uranium enrichment may be used to develop nuclear weapons - which Iran denies.
A nuclear armed Iran "is a threat to the entire region and peace in the world," McCain said.
Sarkozy is expected to announce next month a new force commitment to Afghanistan.