He previously served as the acting assistant secretary of defense for special operations and low-intensity conflict, national security adviser to the United States attorney general and as a former senior director for intelligence programs for the United States National Security Council (NSC).

[4][5] Before joining the White House, Cohen worked for the Defense Intelligence Agency (DIA), beginning in 2010, where he served in Miami, Haiti, Virginia and Afghanistan.

[11] Following Flynn's resignation in February 2017, the new National Security Advisor, H. R. McMaster, attempted to remove Cohen, but he was overruled by Trump.

[12] It is alleged that Cohen inadvertently identified reports suggesting that members of Trump's campaign team had been subjected to incidental surveillance by the United States intelligence community, as part of an unrelated review of privacy procedures.

[20] Upon Cohen's departure, the White House commented that "General McMaster appreciates the good work accomplished in the NSC's Intelligence directorate under Ezra Cohen's leadership... General McMaster is confident that Ezra will make many further significant contributions to national security in another position in the administration.

[23] In May 2017, Cohen and the FBI assistant director for counterintelligence reportedly advocated for strong law enforcement actions against Chinese government officials conducting operations targeting Chinese dissidents and asylum seekers inside the United States, against objections from Acting Assistant Secretary of State Susan Thornton.

Cohen reportedly charged Thornton with "improperly hindering law-enforcement efforts to address China's repeated violations of U.S. sovereignty and law.

[25] In April 2018, he rejoined the Trump administration in the United States Department of Justice, advising then-Attorney General Jeff Sessions on counterterrorism and counterintelligence.

[36] He married Rebecca Miller, who served as deputy assistant secretary for public affairs at the Treasury Department, in November 2016, in a Jewish ceremony.