The two men were turned over by National Liberation Army (ELN) guerrillas in a rural part of northeast Colombia to a humanitarian team that included ICRC delegates, the aid group said in a statement.
The men were identified as Uwe and Otto Breuer, brothers aged 69 and 73. Rebels initially accused the Germans of being spies, but later asked that a humanitarian commission be formed so they could be handed over.
They were kidnapped four months ago in the same region of Norte de Santander department where they were released Friday.
"We're glad that the two men have been freed and will soon be reunited with their families," said Jordi Raich, head of the ICRC delegation in Colombia.
"It's gratifying to be of service in this kind of operation. As an impartial, neutral and independent intermediary between all the parties to the conflict, the ICRC is always keen to help relieve the suffering of people who have been deprived of liberty."
The men were flown by helicopter to the city of Ocana, where they were turned over to German embassy officials before heading to Bogota on a plane, where they were received by the German ambassador and taken to a hotel.
An ICRC assessment determined both brothers were in good health, though tired and depressed after their ordeal, said former attorney Jaime Bernal Cuellar, who was part of the team that obtained the captives' freedom.
The German foreign ministry expressed relief at the release of the hostages and gratitude for the efforts of President Juan Manuel Santos and the ICRC.
"I'm very relieved to know that the two Germans are free again," said Foreign Minister Guido Westerwelle, in the statement.
Santos thanked the ICRC, Bernal, and former governor Horacio Serpa for helping facilitate the release in a post on Twitter.
The ELN is Colombia's second largest rebel army, with an estimated 2,500 fighters.
The FARC, the country's largest guerrilla group with an estimated 8,000 fighters, is holding peace talks with the government.