We investigate the weak cosmic censorship conjecture for Kerr-Sen black holes, which are solutions to
the four-dimensional low-energy effective field theory for the heterotic string theory, based on
the scattering of a charged scalar field. Here, extremal and near-extremal black holes cannot be over-spun and over-charged
in their first-order variations, which is sufficient to conclude that the weak cosmic censorship conjecture is valid for Kerr-Sen black holes.