Armed US marines watched from the embassy roof as students climbed under the gate and over the wall after abandoning their camp, established outside the embassy complex since violent protests began in late April.
The students surged into the embassy compound and began a peaceful sit-in with their hands raised in the air following a police ultimatum demanding they leave their informal camp.
Protests against President Pierre Nkurunziza's controversial third-term bid in elections due next month have left at least 70 dead and forced 100,000 to flee the country.
Burundians are due to go to the polls on Monday to elect parliamentarians with the presidential vote due on July 15.
