The top court's order on Tuesday effectively stayed decisions by trial judges to block the policy, which was first announced by President Donald Trump over Twitter in July 2017.
There are exceptions to the ban, including for those already serving.
The four liberal judges on the court were overruled by the conservative majority. Normally, the Supreme Court only gets ahead of lower courts in cases deemed to be exceedingly urgent.
The court's decision is a win for the Trump administration, though it may be short-lived, and the legal road ahead is likely to be long.
Military officials have told Congress they have not experienced any real problems with transgender individuals in the institution. Those pushing for the courts to overrule the administration's policy say Trump has not presented any information to the contrary.
There are exceptions to the ban, including for those already serving.
The four liberal judges on the court were overruled by the conservative majority. Normally, the Supreme Court only gets ahead of lower courts in cases deemed to be exceedingly urgent.
The court's decision is a win for the Trump administration, though it may be short-lived, and the legal road ahead is likely to be long.
Military officials have told Congress they have not experienced any real problems with transgender individuals in the institution. Those pushing for the courts to overrule the administration's policy say Trump has not presented any information to the contrary.