We perform low-temperature transport and high-resolution photoelectron spectroscopy on 20 nm thin film topological Dirac semimetal Na3Bi grown by molecular beam epitaxy. We demonstrate efficient electron depletion ∼1013 cm–2 of Na3Bi via vacuum deposition of molecular F4-TCNQ without degrading the sample mobility. For samples with low as-grown n-type doping (1 × 1012 cm–2), F4-TCNQ doping can achieve charge neutrality and even a net p-type doping. Photoelectron spectroscopy and density functional theory are utilized to investigate the behavior of F4-TCNQ on the Na3Bi surface.