The protesters shouted pro-Tibet slogans and waved Tibetan flags before they were hauled into police vans and trucks.
Exiled Tibetans have been protesting regularly since a deadly riot broke out in the Tibetan capital Lhasa on March 14 followed by demonstrations in other Tibetan areas of China.
Many Tibetans are furious over the crackdown against protesters in Tibet and resent China's decades-old rule of the Himalayan region.
More than 20,000 Tibetans live in Nepal since fleeing their homeland after a failed 1959 uprising against Chinese rule.
The Lhasa riot broke out after days of protests centred on the anniversary of that uprising.
Tibetans in Nepal briefly suspended protests in May after an earthquake struck China, killing tens of thousands, but demonstrations resumed last week.
Nepal considers Tibet part of China, a key aid donor, and does not allow anti-Chinese protests.