Juan Carlos was kidnapped on December 19th when workers from the charity were travelling between Mazar-e-Sharif city and the volatile Taliban hotbed of Kunduz. Carlos was taken while three of his colleagues were left unharmed.
The International Committee of the Red Cross said Carlos had been returned to their team in Kunduz, but did not say how he was released or who was behind the abduction.
"We are relieved and grateful that Juan Carlos is now back with us, safe and sound," Monica Zanarelli, head of the ICRC delegation in Afghanistan, said in a statement.
"His abduction was a terrible ordeal for him, as well as for his family, friends and colleagues. Our priority now is Juan Carlos' well-being and getting him home to his family."
No militant group has so far claimed responsibility for the abduction.
Local authorities are investigating the incident, Kunduz government spokesman Sayed Mahmood Danish said, without commenting further.
Kunduz faces an intensifying Taliban insurgency as the militants overran its provincial capital in October for the second time in a year.
Kidnapping of foreigners has been on the rise in Afghanistan recently, with criminal gangs staging abductions for ransom or handing the victims over to insurgent groups.
In August, gunmen wearing military uniforms kidnapped two professors of the American University of Afghanistan in the heart of Kabul, underscoring the growing insecurity in the country.
They appeared in a Taliban video that surfaced last week, in the first apparent proof that they were still alive.
And in November, an Australian national was snatched from Kabul, just months after another citizen was rescued after being taken at gunpoint.