Workers at hundreds of Starbucks locations across the US walked out on Thursday during the company’s key Red Cup Day promotional event.

The news was confirmed by the Workers United union, which on X – formerly known as Twitter – said that its members had carried out the largest strike in the Seattle-based coffee chain’s history.

Starbucks’s Red Cup Day is an annual promotion that happens every year at Starbucks locations in the United States and Canada. The event is tied to the launch of the company’s festive menu, with customers who purchase a holiday drink receiving a free reusable red Starbucks holiday cup.

The promotional event is a major driver of traffic to Starbucks stores in the US. Foot traffic to stores during the event in 2022 increased by 94 per cent over the daily average for the year.

The union, which represents more than 9,000 Starbucks staff at around 360 stores, described the event as one of the "most infamously hard, understaffed days" at the ubiquitous coffee chain.

The company said that its stores were open and acknowledged that "a few dozen stores with some partners (were) on strike". The company operates nearly 10,000 stores in the US, with less than 3 per cent represented by a union.

Starbucks has nearly 10,000 U.S. company-owned locations, and according to the company less than 3% of those stores are represented by a union.

Staff walked out at more than 100 locations during the event in 2022.

The company earlier this month said that it would increase pay for US retail workers by at least 3 per cent from 2024. The move was described by workers, who pointed to the company’s 11 per cent increase in fourth quarter revenue, as ‘tone deaf’.

Elsewhere, Starbucks is facing international backlash for suing Workers United over a regional branch of the union publicly displayed solidarity with Palestine on social media. Starbucks is suing for trademark infringement, arguing that its logo is too similar to the company's own.

In a letter to the company, Workers United President Lynne Fox wrote: “Starbucks is seeking to exploit the ongoing tragedy in the Middle East to bolster the company’s anti-union campaign.”

The company however has not been named by the Boycott, Divestment and Sanctions (BDS) campaign.

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