Mendez is replacing Andres Orozco-Estrada, who had to give up the baton for health reasons, according to the Grafenegg culture company.
He will conduct the last concert of the Tonkünstler summer season, which will include works by Richard Strauss, Antonio Pasculli and Ottorino Respighi.
The Spaniard is one of the most respected conductors of the younger generation.
In 2012, he emerged from the Nikolai Malko Competition for Young Conductors in Copenhagen as the winner. In 2013 he was a finalist in the conducting competition of the Salzburg Festival.
During the next season Mendez will work with the Vienna Symphony Orchestra, the Spanish National Orchestra and the Philharmonic Orchestra of Helsinki.