Obama, who is travelling with her mother and daughters, visited the Chengdu Research Base of Giant Panda Breeding in the southwestern province of Sichuan.
There, the Obamas viewed a 22-year-old grandmother panda named Lili as well as five young pandas, according to base staff.
Pictures showed the First Lady using a long stick to pass apples to some of the black and white bears in a grassy enclosure -- next to a sign that warned against feeding them.
The reserve, which was closed to the public for the first familys visit, is home to nearly 80 giant pandas, as well as a colony of red pandas.
Obama and her family had lunch at a Tibetan restaurant in Chengdu, a choice that "was in accordance with (Obamas) interest in the rights of minorities in China", according to White House staff.
The dishes served at the Zangxiang Teahouse featured a heavy emphasis on yak, including yak butter tea, yak soup, yak meat pies and boiled yak ribs.
Sichuan and other provinces neighbouring Tibet are home to a minority of Tibetans, an ethnic group that rights activists say faces religious and cultural repression, underscored by more than 120 self-immolation protests by Tibetans in recent years.
China rejects such criticism and blames the acts on separatist forces led by the Tibetan spiritual leader-in-exile and Nobel peace laureate, the Dalai Lama.
Obama and her family later flew out of Chengdu airport, heading for the US.
Her trip was billed as one focused on "soft" issues rather than on
politics, and the first lady largely stayed true to that pledge, playing ping-pong and jumping rope with students and touring the Beijing sites with her Chinese counterpart Peng Liyuan.
With reporters access highly restricted and interviews with Obama barred during the trip, the potential for any unscripted discussions on areas of disagreement between Beijing and Washington was minimised.
But she touched on politics during her prepared speeches to students, such as on Tuesday, when she promoted ethnic equality and religious freedom in remarks at a Chengdu high school.
"In America, we believe that no matter where you live or how much money your parents have -- or what race or religion or ethnicity you are -- if you work hard and believe in yourself, then you should have a chance to succeed," she told the crowd.
"We also believe that everyone is equal, and that we all have the right to say what we think and worship as we choose," she said.