A Starbucks store in Seattle, the company’s hometown, votes to unionize.

Employees at a Starbucks store in Seattle have voted to unionize, the latest group to do so in a union push that appears to be gaining steam.

The result, announced by the National Labor Relations Board after a count on Tuesday, takes the number of unionized company-owned U.S. stores to seven, out of nearly 9,000. Since Seattle is Starbucks’s hometown and birthplace, the result represents a big gain for Workers United, an affiliate of the Service Employees International Union.

The tally was 9 to 0, and one ballot was uncounted after the company challenged it.

Starbucks’s chief executive, Kevin Johnson, is leaving his post, the company said last week. The company has performed well financially during the pandemic, but management has had to contend with an upswell of criticism from employees — and its stock price is down 30 percent from its peak. Howard Schultz, who oversaw Starbucks’s growth into a global coffee giant, is returning as chief executive on an interim basis, effective April 4.

The company’s leadership has long pursued a union-free model. But after two stores in the Buffalo area voted to unionize in December, more than 100 Starbucks stores in more than 25 states have filed for union elections.

Two employees from the Seattle store spoke at a news conference organized by Workers United after the results were announced. Asked if she had a message for Mr. Schultz, Sydney Durkin, a shift supervisor at the store, said, “If he’s going to come in, expecting his old tactics to work, he’s going to find a whole new reality that is extremely different.”

The other employee, Rachel Ybarra, a barista, said, “We were able to show Starbucks this is a nationwide issue and we are all going to stand for each other.”

Starbucks did not respond to requests for comment.

In November, on a visit to Buffalo, Mr. Schultz sought to respond to the discontent among Starbucks’s partners, the term it uses for its employees. “No partner has ever needed to have a representative seek to obtain things we all have as partners at Starbucks,” he wrote in a letter titled “From Buffalo With Love” that coincided with his visit. “And I am saddened and concerned to hear anyone thinks that is needed now.”

The unionization efforts gained ground as employees cited concerns about understaffing and workplace safety during the pandemic. Starbucks’s legal response suffered a defeat in February, when the National Labor Relations Board in effect ruled that employees could unionize store by store.

The union victories at Starbucks come as inflation is eroding the purchasing power of wages and as economists expect workers to press for higher pay. In its annual report, released in November, Starbucks warned, “If a significant portion of our employees were to become unionized, our labor costs could increase and our business could be negatively affected by other requirements and expectations that could increase our costs, change our employee culture, decrease our flexibility and disrupt our business.”