The 27-year-old Czech rider was a 125cc frontrunner in the mid-2000s, with fourth in the '07 championship his career highlight.
He last raced at world championship level in Moto2 in 2010, and has since been limited to partial programmes in Spanish and German domestic series and a brief World Supersport appearance.
Team boss Giampiero Sacchi said: "Lukas's return is very welcome - he wrote some great pages of Derbi's history in 125cc working alongside some of our current team members.
"It's a tough challenge lying ahead of him but I'm sure he can do well in the premier class."
Pesek joins existing Ioda rider Danilo Petrucci in the squad.
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