The Colombian midfielder is over the moon to have joined the Nerazzurri and says he is eager to remain at the club for the foreseeable future
The Colombia international joined the Nerazzurri on loan in January with a view to a permanent deal after falling down the pecking order at Porto under Vitor Pereira.
Guarin only made his Inter debut in the 5-4 win over Genoa last Sunday because of a calf problem, but the 25-year-old midfielder is determined to convince the Nerazzurri to buy him outright in the summer.
"The fact that Inter decided to sign me when I was injured was a big motivation for me, and I want to repay this trust on the field," he told Inter Channel.
"Inter are a dream to me, this is like a fairytale. I am excited to be here and wear the shirt of such an important club after I had such a difficult childhood.
"I am here with the motivation to remain at this club for many years."
Inter, who lie in seventh position in the Serie A standings, will visit Cagliari on Saturday.