The two men reportedly had a final farewell chat on Wednesday.
McGahn was also a personal friend of newly confirmed Supreme Court Justice Brett Kavanaugh.
US president Donald Trump has said he will not accept the blame if his party loses control of the US House of Representatives in November, arguing that his campaigning and endorsements have helped Republican candidates.
Despite the turmoil, McGahn had great success in getting President Donald Trump's judicial choices through the Senate.
His departure is no surprise.
Mr Trump offered a defence for the USA ally, warning against a rush to judgment, similar to what he said happened with his U.S. supreme court nominee, Brett Kavanaugh, who was accused of sexual assault.
During his time as White House counsel, McGahn repeatedly butted heads with Trump and occupied a position rife with potential conflicts.
"Well, I do like Congress", he added.
Finnish Orthodox Church hopes to maintain ties with Moscow Patriarchate
Apart from that, the holy synod of the Russian Orthodox Church hopes that there will be no clashes in Ukraine over this issue. The Synod of the Russian Orthodox Church (ROC) stopped "eucharistic communication" with the Patriarchate of Constantinople .
As White House counsel, McGahn took on a handful of often-conflicting roles: counselor to the president; protector of top law enforcement officials, including the special counsel, Robert Mueller; and witness in the investigation into whether Trump obstructed justice.
McGahn's job will be filled by Pat Cipollone.
In a wide-ranging interview three weeks before Election Day, Trump told The Associated Press he senses voter enthusiasm rivaling 2016 and he expressed cautious optimism that his most loyal supporters will vote even when he is not on the ballot.
Cipollone's law firm notes that he is experienced in "a wide variety of cases, including complex maters" such as class action lawsuits, regulatory disputes involving federal agencies, congressional investigations and financial matters.
Emmet Flood, who replaced Trump lawyer Ty Cobb in May, will continue to be the point of contact between Trump's legal team and Mueller's Russian investigation.
"I don't believe anybody has ever had this kind of impact", he added.
Trump's counsel Jay Sekulow praised the decision to hire Cipollone to fill McGahn's role. "If selected by the President, he would make an outstanding White House counsel", Sekulow said.