In this paper rationalized Haar (RH) functions method is applied to approximate the numerical solution of the fractional Volterra integro-differential equations (FVIDEs). The fractional derivatives are described in Caputo sense. The properties of RH functions are presented، and the operational matrix of the fractional integration together with the product operational matrix are used to reduce the computation of FVIDEs into a system of algebraic equations. By using this technique for solving FVIDEs time and computational are small. Numerical examples are given to demonstrate application of the presented method with RH functions base. In this paper rationalized Haar (RH) functions method is applied to approximate the numerical solution of the fractional Volterra integro-differential equations (FVIDEs). The fractional derivatives are described in Caputo sense. The properties of RH functions are presented، and the operational matrix of the fractional integration together with the product operational matrix are used to reduce the computation of FVIDEs into a system of algebraic equations. By using this technique for solving FVIDEs time and computational are small. Numerical examples are given to demonstrate application of the presented method with RH functions base.