Summary: The \((k - 1)\)-fault diameter \(D_k(G)\) of a \(k\)-connected graph \(G\) is the maximum diameter of an induced subgraph by deleting at most \(k - 1\) vertices from \(G\). This paper considers the fault diameter of the product graph \(G_{1}*G_{2}\) of two graphs \(G_{1}\) and \(G_{2}\) and proves that \(D_{k_{1}+k_{2}}(G_{1}*G_{2}) \leqslant D_{k1}(G_{1})+D_{k2}(G_{2})+1\) if \(G_{1}\) is \(k_{1}\)-connected and \(G_{2}\) is \(k_{2}\)-connected. This generalizes some known results such as Banič and Žerovnik [I. Banič and J. Žerovnik, “Fault-diameter of Cartesian graph bundles”, Inf. Process. Lett. 100, No.2, 47–51 (2006; Zbl 1185.05121)].