Krol replaces Frenchman Sebastien Desabre, who has taken up the role of technical director.
Krol quit as coach of CS Sfaxien in November after taking them to the African Confederation Cup title.
Last May he was at the helm of Sfaxien as they pipped Esperance for the Tunisian league title.
He also served as caretaker coach of Tunisia when they played against Cameroon in the World Cup qualifying playoff in October and November. Cameroon won the tie 4-1 on aggregate.
Esperance, the most successful club in Tunisian league history, and Sfaxien will represent Tunisia in this year's African Champions League, which kick off next month.