Labor Secretary Marty Walsh said Thursday he would leave the department in mid-March.

Walsh, a union construction worker who rose to be mayor of Boston and then Labor secretary, in an email to department staff touted the work during his tenure to promote collective bargaining and union organizing. He didn’t confirm that he would become the union leader for professional hockey players, but the National Hockey League Players’ Association separately said its executive board had unanimously appointed Walsh as executive director.

“We promoted every worker’s right to form a union, rallied the entire federal government to advance labor rights, and provided critical information and support to workers during a historic surge in union organizing activity,” Walsh said in his email. “I’ve met with workers at their workplaces, in union halls, and on a picket line, and I’ve sat at the table and spent long nights with labor and management to get to solutions.”

Walsh in the note to staff also praised the work of Labor Deputy Secretary Julie Su, whom the Congressional Black Caucus has pushed as his replacement. 

“Julie is an incredible leader and has been central to our success as a team and as a Department. With the kind of leadership and talent assembled across the Department, I am confident there will be continuity and the work will be sustained,” he said. 

During Walsh’s tenure, the department finalized rules related to health care and the management of retirement funds. The department finalized a rule allowing retirement fund managers to consider environmental, social and governance factors when making investment decisions, reversing a rule established during the Trump administration. 

The department also finalized rules related to health insurance, including a final rule implementing surprise billing provisions included in the fiscal 2021 spending omnibus, and is considering a proposal that would make contraception more accessible when employers deny coverage.