Gary Locke's three-day local government-organised trip in and around the region's capital, Lhasa, with members of his family and embassy staff ends tomorrow.
US Embassy deputy spokesman Justin Higgins said it was the first time Chinese authorities had approved an embassy request to visit Tibet since September 2010.
The embassy said that in his meetings, Locke lobbied for opening access to Tibet to foreign diplomats, journalists and tourists and stressed the "importance of preserving the Tibetan people's cultural heritage, including its unique linguistic, religious and cultural traditions."
More than 100 Tibetans have set themselves on fire since 2011 to protest Chinese policies in the region and call for the return of the Dalai Lama, their beloved spiritual leader, from exile.
"We remain concerned by the deteriorating human rights situation in Tibetan areas, including the tragic self-immolations," Higgins said.
The US urges Beijing to "engage in substantive dialogue with the Dalai Lama or his representatives without preconditions," he said.