The La Liga side have beaten off the reported interest from Chelsea and Real Madrid to land the Colombia international for a fee that's capable of rising to £40.7m
The Portuguese champions announced the sales to the Portuguese stock market (CMVM), and added that both transfers are only subject to the completion of routine medical exams.
While Ruben Micael makes the switch for €5m [£4.3m], Falcao joins Atletico in a deal worth €40m [£34.7m], with the fee for the Colombian striker capable of rising to as much as €47m [£40.7m] depending upon his performances for the club.
Falcao's transfer to the Vicente Calderon brings to an end one of the summer's most drawn-out sagas, after the striker publicly aired his wish for a bigger challenge at the end of last season.
Real Madrid and Chelsea were both reported to be interested in Falcao after he scored 38 goals in all competitions last season to help Porto win a treble of Portuguese League, Portuguese Cup and Europa League.
However, neither club came knocking for the player, leaving the path open for Atletico, who were looking for a new attacker following Sergio Aguero's move to Manchester City.
Falcao's transfer fee falls €5m [£4.3m] short of his release clause, but the inclusion of Ruben Micael in the deal leaves both clubs happy with the outcome of negotiations.
The Portugal international, who cost Porto €3m [£2.6m] in January of 2010, was never able to affirm himself at the Estadio do Dragao, and Steve Defour's signing from Standard Liege further pushed him down the club's pecking order.