In the present manuscript, we discuss the existence, uniqueness an Ulam-stability of solutions for sequential fractional pantograph equations involving $n$ Caputo and one Riemann-Liouville $q-$fractional derivatives. We prove the uniqueness of solutions for the given problem by using Banach's contraction mapping principle. Then, the existence of at least one is obtained via Leray-Schauder'salternative. Also, we define and study the Ulam-stability of solutions for the considered problem. Finally, an example is also given to point out the applicability of our main results.
