In braneworld models coming from string theory one generally encounters massless scalar degrees of freedom -moduli- parameterizing the volume of small compact extra-dimensions. Here we discuss the effects of such moduli on Newtons law for a fairly general 5-D supersymmetric braneworld scenario with a bulk scalar field $phi$. We show that the Newtonian potential describing the gravitational interaction between two bodies localized on the visible brane picks up a non-trivial contribution at short distances that depends on the shape of the superpotential $W(phi)$ of the theory. In particular, we compute this contribution for dilatonic braneworld scenarios $W(phi) = e^{alpha phi}$ (where $alpha$ is a constant) and discuss the particular case of 5-D Heterotic M-theory.