This article presents a numerical method for solving nonlinear two-dimensional Volterra–Fredholm integro-differential equations of the second kind. Here, we use the so-called two-dimensional triangular function, First, the two-dimensional triangular operational matrix of integration and differentiation has been presented, then by using this matrices, the nonlinear two-dimensional Volterra–Fredholm integro-differential equation has been reduced to an algebraic system. Finally, some numerical examples are given to clarify the efficiency and accuracy of the presented method.