In optics, Brewster’s effect is an important phenomenon widely used in photonics and laser physics to control radiation polarization at the interface between two dielectric media. In this work, we show that the Brewster effect is clearly evident when light passes through a small nanohole made in a thick metal film (zero-mode waveguide, ZMW). We develop a model to describe this phenomenon, involving increased excitation efficiency of the dipole moment associated with the ZMW at a specific angle – the Brewster angle – at the metal/dielectric interface. At this angle, the transmittance for p-polarized light through the ZMW is about 20 times higher than for s-polarized light, opening new possibilities for applications of ZMW in single-molecule microscopy methods.