As a late-morning stream of customers lined up at the Darwin’s Ltd. coffee shop in Cambridge, barista Sam White stepped back from the espresso machine and made an announcement.

“Attention customers,” White began, as a hush fell over the shop. “We’re going to take a little break. We apologize to all of you in line for making you wait a little bit extra for your order today, but everything would run much more smoothly here if we had a real say on the job, if we were paid enough. … We hope you understand.”

In a coordinated effort across all four Darwin’s locations, employees emerged from behind the bar and walked out to protest delays in their unionization process. A small group of pro-union workers from other local coffee shops joined them on the sidewalk on Cambridge Street.

Last September, about 36 workers at Darwin’s cafes filed a petition to unionize, hoping to become the second independent coffee chain in Massachusetts to form a union, following a petition by Pavement Coffeehouse workers earlier that year. Workers said management has since been slow to schedule bargaining sessions and reluctant to negotiate a contract — delays that workers describe as a “union-busting tactic.”

Members of the cafe’s organizing committee on Tuesday met with management for their first bargaining session in seven weeks. While that meeting was occurring, Darwin's workers walked out for a simultaneous seven-minute break, a number signifying solidarity with the Memphis Seven, a group of Starbucks employees who were fired while seeking to unionize last month in Memphis. Starbucks has denied that those firings were related to the union effort.

“Management has stalled and has been refusing to engage and respond to our proposals,” White said. “We know that the only thing that’s going to make them listen is if we show that we are ready to act as a union, as one. That’s what today represents.”

Darwin’s owner Steve Darwin, who met with workers Tuesday for contract negotiations, did not immediately respond to a request for comment.

“If the Union has a written support of a majority of our employees, Darwin’s will recognize the Union and begin negotiations for a contract,” the cafe chain said in a social media post in September.

On the sidewalk outside the Cambridge Street shop, workers from Darwin’s stood beside baristas from Pavement Coffeehouse and pro-union Starbucks locations, holding signs reading “a living wage before tips” and “rebuild the labor movement.”

A growing number of workers in the coffee shop industry have coordinated efforts across Massachusetts, with members represented by unions including NEJB Unite Here, Workers United and others.

“We are one industry, and having the support from coffee workers all around Boston is just really important to show that solidarity and help out where we can,” said Angie Muse, a barista at Pavement’s Allston location. “We all communicate with each other in case anybody needs anything, or for instances like this.”

Ty Nolan, a barista at a Starbucks location in Lower Allston that began an effort to form a union last January, said efforts to unionize vary between small and large stores. He critized delays in reaching agreements on union contracts.

“While [Darwin’s] union was immediately recognized, they've still been facing forms of union busting through the negotiation process,” Nolan said. “If they're going to show solidarity with us, I think it's really important we stand with them as well.”