Stochastic volatility models for option pricing are suitable to explain many empirical stylized facts in financial markets. Among the other models, Heston provides a good analytical tractability because a quasi closed formula for the price of a European call option can be derived. The estimation of the Heston model parameters is nowadays a subject of on-going research; the aim of this paper is to manage uncertainty about parameters through fuzzy logic preserving the probabilistic structure of the Heston model.