The Pamplona-based club have secured the services of the 26-year-old Argentine, who struggled to make his mark at the Ramon Sanchez Pizjuan since joining in 2007
The Argentine midfielder has signed a contract with the Pamplona-based club for the next three years after becoming a free agent at the end of last season.
Armenteros, who will be officially unveiled to the press on Tuesday, joined Sevilla in 2007 but failed to hold down a place at the two-time Uefa Cup winners and has spent the last two years on loan at Rayo Vallecano.
He has become Osasuna's fourth signing of the summer, following in the footsteps of Nano, Sisi and Arribas.
The Navarrans finished seventh in La Liga last term, just one point below the Europa League qualification places.