Nielsen was former DHS Secretary John Kelly's deputy when he served in that role and moved with Kelly to the White House when he was tapped to be Trump's chief of staff.
Nielson worked for former President George W. Bush on the White House Homeland Security Council and also previously headed legislative policy and government affairs at the Transportation Security Administration (TSA), which is part of DHS. Her supporters say she has been trying to help professionalize the White House.
"I call upon the Senate.to confirm this tremendously qualified and talented nominee", Trump said during a ceremony in the East Room of the White House.
"There will be no on-the-job training", he said.
Mr. Kelly is one of the top officials who have been advocating for her selection for quite some time.
Trump declared his option in a disclosure that considered Ms. Nielsen's sizeable competent wisdom in the domain of homeland security policy and procedure, cyber security, crucial infrastructure and exigency management.
Though the White House confirmed her nomination, the president gave an on-camera announcement Thursday afternoon. Elaine Duke has been serving as acting DHS secretary since then.
Rep. Bennie Thompson (D-Miss.), a ranking member of the House Homeland Security panel, said he was pleased Trump had selected a permanent agency head "after letting the critical national security position remain vacant as the nation faced multiple major hurricanes and a domestic terrorism attack".