The Portuguese club said in a statement to the Lisbon stock exchange that the price tag could rise to 47 million ($67 million) depending on variable factors it did not specify.
Falcao—nicknamed “El Tigre” (The Tiger)—was a key player for Porto last season, scoring 34 goals to help it win four trophies, including the Portuguese title, in a 30-game unbeaten league run.
Falcao will step in to fill the role vacated by Argentina striker Sergio Aguero, who joined Manchester City in a 38 million pound ($62 million) deal last month.
The 25-year-old Falcao scored the only goal in the Europa League final in Dublin to set a record of 17 goals scored in Europe’s second-tier competition. Chelsea was also reportedly interested in Falcao since coach Andres Villas-Boas had coached the Colombian last season at Porto.
Porto paid Argentine club River Plate ?3.93 million ($5.5 million) for Falcao in 2009.
Porto said it is also selling Portugal midfielder Ruben Micael to Atletico for ?5 million ($7 million). Atletico said Micael had agreed to a four-year deal and was set to be loaned out to Spanish club Zaragoza for the season.