The coffee chain appointed labor relations expert Thomas Mackall in March on a request by shareholders to look into its labor practices following complaints to the National Labor Relations Board (NLRB) by some employees and labor groups.
They had accused Starbucks of engaging in "union-busting" activities when workers sought better wages, staffing and schedules.
The inquiry conducted from July to September called on Starbucks to improve the way it engages with unionization and revise its Global Human Rights Statement, but said there were no sign that it interfered with the freedom of employees to unionize.
"The assessment was direct and clear that while Starbucks has had no intention to deviate from the principles of freedom of association and the right to collective bargaining, there are things the company can, and should, do to improve its stated commitments," said Mellody Hobson, independent chair of Starbucks.
The Starbucks Workers United union, which represents more than 9,000 employees at about 360 U.S. stores, said the report "acknowledges deep problems" in the company's response to unionization by workers.
"If the company's efforts at dialogue over the last few days are sincere, we are ready to talk," the union said.
Starbucks last week reached out to the union and proposed to resume with a set of representative stores in January.
The NLRB declined to comment.
