The Nerazzurri have exercised their buying option for the 25-year-old, who spent the second half of the 2011-12 campaign on loan at the San Siro outfit
The Colombia international joins the Serie A side on a permanent basis after impressing on loan for the Nerazzurri, despite the fact that a calf problem restricted him to just six appearances for the club.
According to Porto, Inter have splashed out €11 million to secure the services of Guarin, who was on the fringes of the action at the Estadio do Dragao during the first half of the season.
"The completion of the deal is now dependent upon the player signing a contract with Inter," a Porto statement read.
Guarin's agent revealed on Wednesday that his client had been on Inter's wish list "for two years".
The 25-year-old midfielder, who joined Porto from Saint-Etienne in 2008, has 36 international caps to his name, scoring two goals in the process.
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