The 23-year-old has signed a five-year contract with Sporting Lisbon and joins the club in a €3.7million deal.
Jeffren reportedly has a €30million buy-out clause inserted into his deal.
Jeffren said: “Sporting are a great club. I am proud to be able to represent this club. I am very happy with the trust they have in me. My goal is to grow in this team. I can grow and evolve, to become a better player.”
