Labor Secretary Tom Perez announced the changes in a memo to the department’s staff on Friday, calling the Supreme Court’s June decision in United States v. Windsor, which struck down the Defense of Marriage Act, “a historic step toward equality for all American families.” The changes represent early victories for gay-rights advocates who have been pressing the Obama administration to issue guidance for employers and employees about the ruling and to launch an effort to eventually write new regulations that would further expand rights for same-sex married couples.

Mr. Perez said the guidance on the Family and Medical Leave Act is “one of many steps” the Labor Department will take over the coming months to implement the high-court decision. He said he has directed heads of agencies within the department “to look for every opportunity to ensure that we are implementing this decision in a way that provides the maximum protection for workers and their families.”

Employment lawyers have said for weeks that the Supreme Court ruling automatically makes same-sex couples eligible for leave to care for their spouse under the FMLA—as long as they live in Washington, D.C., or one of the 13 states that recognize gay marriage.