Morell announced his retirement Wednesday after 33 years in the CIA, saying he wants to devote more attention to his family, The Washington Post reported.
CIA Director John Brennan said Morell will be replaced in August by CIA outsider Haines, who previously acted as a White House lawyer.
Though Haines, 43, has never worked inside the intelligence agency, "she knows more about covert action than anyone in the U.S. government outside of the CIA," Brennan said.
"She has participated in virtually every Deputies and Principals Committee meeting over the past two years and chairs the Lawyers' Group that reviews the agency's most sensitive programs," he added, in a statement.
Obama nominated Haines two months ago as legal counsel for the State Department. She also worked as deputy counsel for the Senate Foreign Relations Committee, the Post reported.