This study examined sex differences in the discrimination of minimal pairs of foreign language (non-native) tonemes. Adult native speakers of English (237 women and 177 men), with no prior exposure to a tonal language, performed an AX-task, which required them to discriminate between rising and falling-rising Norwegian tonemes. When controlling for nonverbal intelligence, prior exposure to foreign languages, and age, sensitivity measures (A’) showed a clear male advantage. Thus, the sex differences previously observed in non-linguistic temporal processing tasks appear to extend to the discrimination of unfamiliar non-native speech sounds. These sex differences in auditory processing may be due to anatomical differences between men and women in the ratio of white to grey matter in the left hemisphere, which, in turn, might affect speed of neural transmission. These findings contribute to the ongoing debate on cognitive effects of putative sex differences in intra- and inter-hemispheric connectivity.