This paper deals with the computation of differentiation matrices on plane domains. To this end, the proposed numerical scheme is built using collocation approximation based on domains unstructured meshes. Here, Gauss-Lobatto collocation points on a reference triangle are used. Then, with some appropriate transformations, collocation points are generated on the whole considered domain. Also, the algorithm for approximating differentiation operators by means of collocation points is given. Numerical examples show the high accuracy of the proposed scheme.