This study examined the influence of sad mood on the judgment of ambiguous facial emotion expressions among 47 healthy volunteers who had been induced to feel sad (n=13), neutral (n=15), or happy (n=19) emotions by watching video clips. The findings suggest that when the targets were ambiguous, participants who were in a sad mood tended to classify them in the negative emotional categories rather than the positive emotional categories. Also, this observation indicates that emotion-specific negative bias in the judgment of facial expressions is associated with a sad mood. The finding argues against a general impairment in decoding facial expressions. Furthermore, the observed mood-congruent negative bias was best predicted by spatial perception. The findings of this study provide insights into the cognitive processes underlying the interpersonal difficulties experienced by people in a sad mood, which may be predisposing factors in the development of clinical depression.