"I am getting threats on a regular basis. Not only is my life in danger, my family is also in danger. I have therefore decided to quit," lawyer Samiullah Afridi said.
Afridi is representing Dr Shakil Afridi, who was jailed for 33 years after helping the CIA find the al-Qaida chief. Bin Laden was hiding in Pakistan until US Navy Seals killed him in a 2011 raid.
The raid - and Dr Afridi's jail sentence - severely strained relations between the United States and Pakistan, its nominal ally.
Afridi's sentence was later overturned. He is still in jail and undergoing a retrial, but his lawyer said the US government was unduly interfering.
"The government of America is putting a lot of pressure on the Pakistani government for the release of Dr. Shakil Afridi," he said.
"Our mission and our wish also was to get him released, but our courts are free and they have to work according to a set procedure. I therefore did not like America's unjustified pressure."
A US embassy spokeswoman was not immediately able to comment on the allegations.
Relations between two allies were icy after the bin Laden raid.
Pakistan's powerful army was furious that the United States had mounted a military operation on its soil without advance warning. In turn, some US leaders were suspicious that Pakistani security forces may have helped shield bin Laden.
After it emerged that Afridi had run a fake vaccination campaign in an effort to help the CIA find bin Laden, Pakistani authorities jailed him for alleged links to militants.
The sentence provoked outrage in the United States and the government cut a symbolic $33 million from an aid package to Pakistan.
Several militant groups, including the Taliban, have threatened to kill Dr Afridi if he is ever released.