The Americans were among some 50 people, including U.S., British, Canadian, Belgian and Congolese citizens, who stood trial last year following the botched attempt to overthrow the government in May.
A total of 37 defendants were sentenced to death by a military court in September, including U.S. citizens Marcel Malanga, Tyler Thompson and Benjamin Zalman-Polun.
All three were found guilty of criminal conspiracy, terrorism and other charges.
They denied any wrongdoing and unsuccessfully appealed against the verdict. But Congo's justice ministry then proposed a pardon, which the public prosecutor requested from the presidency.
President Felix Tshisekedi on Tuesday signed three orders to commute their sentences to life in prison, his spokesperson Tina Salama said on national television.
"This presidential pardon is a first step that promises major changes in the future," one of Malanga's lawyers, Ckiness Ciamba, said by telephone.
Relatives of Malanga and a lawyer for Zalman-Polun did not immediately respond to requests for comment. Thompson's parents declined to speak on the record.
Marcel Malanga is the son of U.S.-based Congolese politician Christian Malanga, who led the armed men who briefly occupied an office of the presidency in the capital Kinshasa on May 19 before security forces killed him.
Thompson is a friend of Marcel Malanga who played high school football with him in Utah. Both are in their 20s. Zalman-Polun was a business associate of Christian Malanga.
Their sentences were commuted ahead of a trip to Congo by the newly appointed U.S. senior advisor for Africa, Massad Boulos.
Boulos, the father-in-law of U.S. President Donald Trump's daughter Tiffany, will travel to Congo, Rwanda, Kenya and Uganda from April 3, the State Department said in a statement on Tuesday.
He will seek to advance efforts for peace in east Congo, where a Rwanda-backed rebellion is raging, and promote U.S. private sector investment in the region.
(Reporting by Ange Kasongo, Sonia Rolley and Stanis BujakeraAdditional reporting by Jessica Donati in Dakar Writing by Sofia ChristensenEditing by Robbie Corey-Boulet, Aidan Lewis)

Marcel Malanga (C), and some of the 51 defendants on trial for 'coup attempt' sits in the military court to hear their verdict in Ndolo military prison in Kinshasa, Democratic Republic of Congo, 13 September 2024. The military court is due to rule on the 'coup attempt' that the Democratic Republic of Congo army says it foiled in May 2024. Some 51 individuals, including three Americans, are on trial for attempting to overthrow the president of the Democratic Republic of Congo on 19 May 2024. Six people were killed during the attempted coup including the suspected leader of the plot, Christian Malanga. They are charged with 'attack, terrorism, illegal possession of weapons and war munitions, attempted assassination, criminal association, murder and financing of terrorism', according to the military court president. EPA-EFE/CHRIS MILOSI