The Tibetans were stopped by Nepali police as they were driving to the border, and were arrested as they were continuing on foot, the witnesses said.
The activists waved placards and shouted anti-China slogans and said they were protesting Chinese suppression of Tibetan people.
Police said 26 men and eight women were picked up from Balesi in Sindhupalchowk district, near the Friendship Bridge which lies on Nepal´s border with China.
"We are going to keep them in police custody until we hear from our headquarters," said police officer Abhaya Joshi.
Nepal is home to around 20,000 exiled Tibetans, who began arriving in large numbers in 1959 after their spiritual leader the Dalai Lama fled China into exile in India.
Sandwiched between India and China, Nepal has upheld Beijing´s "one China" policy that Tibet is an integral part of China, and has repeatedly said it will not tolerate anti-China demonstrations as it seeks to preserve friendly ties with its northern neighbor.
Authorities maintained tight security this year to quell any possible unrest related to the 50th anniversary of the failed uprising in Tibet which led to the Dalai Lama´s departure.
Worldwide protests erupted last year after China cracked down on demonstrators in Tibet marking the March 10 anniversary of the 1959 uprising.
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