Sullivan currently serves as the assistant secretary of public and intergovernmental affairs at the Department of Veterans Affairs. A Marine Corps captain, Sullivan is a veteran of the Iraq war and a graduate of both Harvard Business School and the Kennedy School.

"I am thrilled to have Maura Sullivan joining the Department of Defense as the assistant to the secretary of defense for public affairs," Carter said in a statement. "Her life of service and leadership, both in and out of uniform, make her uniquely qualified to run the Pentagon's public affairs team during this crucial time for the nation and the department."

Sullivan is replacing Brent Colburn, who is stepping down in July before pursuing "an opportunity outside of government," the release said.

The announcement comes just days after Carter named Peter Cook, currently of Bloomberg TV, as his press secretary. Cook, who is filling a spot left empty since Adm. John Kirby stepped down from the position early in Carter's tenure, will begin in July.

It also coincides with the departure of Army Col. Steve Warren, who has been director of Defense Press Operations since August of 2012. Warren has served as the chief spokesman for the Pentagon in Kirby's absence.

Twitter: @AaronMehta