Representatives of allied activist groups from Canada, Europe and Taiwan made remarks and led the attendees in chants of "Fight for freedom! Stand with Hong Kong!"
Speakers also celebrated the results of Saturday's presidential election in Taiwan that saw the Democratic Progressive Party's Tsai Ing-wen voted to a second term in a landslide.
Months of anti-government protests in Hong Kong, a semi-autonomous Chinese territory, have driven home to many in Taiwan the contrast between their democratically governed island and authoritarian mainland China.
A former British colony, Hong Kong was returned to China in 1997. Under the framework of "one country, two systems," the city enjoys greater democratic rights than those on the mainland, but protesters say those freedoms have been steadily eroding under Chinese President Xi Jinping.