We investigate the effect of uncertainty principle on the simulation of quantum transport based on the Wigner function. We show that due to the positional uncertainty of electrons within the device, which bounds the region for nonlocal potential correlation, a constraint is imposed via the uncertainty principle on the possible momentum resolution of the Wigner function. It is numerically demonstrated that its violation deteriorates the simulation results significantly in configurations where the quantum effects are crucial. (C) 2015 Elsevier Ltd. All rights reserved.