The protests, organised by a movement of grassroot groups, were held in 136 cities and towns across six continents, from Soweto to San Francisco and Tokyo.
In South Africa, which is struggling to stem a rhino poaching crisis, demonstrators gathered in 17 cities.
"We are protesting against the political leaders of the world who do not have the guts and political will to make changes in their laws," Dex Kotze, one of the march organisers, told AFP.
From 27 million elephants 350 years ago, Africa now has about 400,000 left, and roughly nine percent of those are being killed each year, Kotze said.
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South Africa, home to the world's largest population of rhinos, has seen at least 700 killed so far this year. The poaching of the rare African animal is increasing to meet demand from Asian countries where the rhino horn has long been used in traditional medicines for a variety of ailments, including fever and rheumatism.
Kotze said the protests meant to highlight the so-called gang-of-19 countries listed by CITES, the international regulatory body for trade in wildlife, as not doing enough to curb trafficking.
Among the countries are China, Vietnam, Laos, Mozambique, Angola and Kenya.
"These countries need to change their laws," he said.
Kotze took aim at China and warned that if it does not shut its 37 ivory carving factories and 130 retail outlets, "we will lose all the elephants".