Environmental stress can lead to a decrease in the body size of insects. As social insects, ants have a complex caste system; each caste has its own morphological traits and functions in the colony, hence the effects of stress may manifest differentially among different ant castes. Here we investigated the body size of males of the common garden ant, Lasius niger L., 1758, living in a postmining area polluted mainly by Zn, Cd, and Pb. We examined if individual body size decreases with the pollution gradient. The ants were sampled from 39 wild colonies originating from 17 sites located along the metal pollution gradient; head width was used as the estimator of body size. We failed to show a significant correlation between pollution and male body size, indicating no direct effect of pollution on the body size of males of the investigated ant. However, we found a significant dependence with the colony of origin, which is in line with a previous study performed on this species in unpolluted sites. These results further strengthen a general conclusion that morphological traits in ants, such as body size or fluctuating asymmetry, are relatively invariable and stable across gradients of metal pollution.