The 23-year-old Spaniard makes the switch after scoring five goals in 25 appearances for his parent club.
"We've been trying to wrap up the deal for a good while," explained Eintracht sporting director Bruno Hübner, "so it feels even better now it's finally gone through. We're convinced Joselu has the quality the team needs to push on. He fits our profile perfectly."
Joselu, who learned his craft in his native Spain with Real Madrid and Celta Vigo, can't wait to get the next chapter in his career under way. "From the start, Bruno Hübner und Armin Veh gave me the feeling that they could really use me in the team," he said. "I'm sure it's the right move for my career and I'm really looking forward to making my first start for the Frankfurt Eagles."