The ability to recognize subtle facial expressions can be valuable in social interaction to infer emotions and intentions of others. Research has shown that the personality trait of alexithymia is linked to difficulties labeling facial expressions especially when these are presented with temporal constraints. The present study investigates the neural mechanisms underlying this deficit. 50 young healthy volunteers had to label briefly presented (≤100ms) emotional (happy, angry, fearful) facial expressions masked by a neutral expression while undergoing functional magnetic resonance imaging (fMRI). A multi-method approach (20-Item Toronto Alexithymia Scale and Toronto Structured Interview for Alexithymia) was administered to assess alexithymic tendencies. Behavioral results point to a global deficit of alexithymic individuals in labeling brief facial expressions. Alexithymia was related to decreased response of the ventral striatum to negative facial expressions. Moreover, alexithymia was associated with lowered activation in frontal, temporal and occipital cortices. Our data suggest that alexithymic individuals have difficulties in creating appropriate representations of the emotional state of other persons under temporal constraints. These deficiencies could lead to problems in labeling other people׳s facial emotions.