Ricker Hamilton has worked for the agency since 1982 and plans to retire at the end of the month.
Hamilton's departure comes at a time when DHHS is revamping its child protective services in the wake of the deaths of two young girls.
He released a statement saying it has been his honor serving the people of Maine for the last 41 years and that his is proud of what the department has accomplished, including its response to the opioid epidemic.
Governor Paul LePage has appointed Bethany Hamm acting director once Hamilton leaves. She currently is director of the Office of Family Independence.