Xi had not been seen in public since September 1 and cancelled meetings with four foreign dignitaries including US Secretary of State Hillary Clinton, giving rise to intense speculation about his health.
The vice president arrived at China Agricultural University Saturday morning for "activities marking this year's National Science Popularisation Day", state-run news agency Xinhua said.
His unexplained disappearance came at a highly sensitive time for China, which is gearing up for a generational handover of power.
On Thursday, he made his first public communication in nearly two weeks when state media said he had "expressed condolences on the death of old party comrade Huang Rong", who died on September 6 -- a day after Xi missed a planned meeting with Clinton.
The report in the Guangxi Daily newspaper -- mouthpiece of the Communist Party committee in China's southern Guangxi region -- marked the first public communication by Xi since he delivered a speech on September 1.
The news was published widely in China, but made no mention of Xi's health, which has been the subject of widespread speculation in recent days. Theories about his health have mentioned anything from back ache to a heart attack.
Xi has been widely tipped to succeed President Hu Jintao as leader of the ruling Communist Party at a crucial meeting that is expected to be held sometime next month, before taking over as head of state in March.
His disappearance from public view has attracted global attention, as well as some speculation on China's popular but heavily censored microblogs.
