Abstract. We study a cubic Dirac equation on R × R 3 i∂tu + Du + V (x)u = βu, u βu perturbed by a large potential with almost critical regularity. We prove global existence and scattering for small initial data in H 1 with additional angular regularity. The main tool is an endpoint Strichartz estimate for the perturbed Dirac flow. In particular, the result covers the case of spherically symmetric data with small H 1 norm.When the potential V has a suitable structure, we prove global existence and scattering for large initial data having a small chiral component, related to the Lochak-Majorana condition.