More than 40 protesters held an hour-long working conditions "teach-in" outside the Burger King outlet at Aotea Square in Auckland yesterday.
After the speeches, two protesters tried to enter the store but found the door blocked by security guards.
The Unite union national director, Mike Treen, said the protest was to speak up for the company's workers about a culture of exploitation over pay and individuals being intimidated not to join the union.
Three-quarters of the staff were migrants and students and a series of teach-ins around the country would show support for "young, vulnerable workers".
Burger King NZ was resisting signing a collective agreement with the union and was the last major fast-food chain without one, he said.