Following a prayer, Noem strutted to the podium to applause as the country hit played.
Noem, who held her state's lone US House seat for eight years before becoming governor in 2019, has risen in the Republican Party by tacking closely with Trump.
At one point, she was even under consideration to be his running mate.
Noem addressed the DHS employees on Tuesday afternoon, having participated in US Immigration and Customs Enforcement raids earlier in the day.
In a post to X, Noem, dressed as an ICE agent, told the camera, “We are getting the dirtbags off these streets.”