Although the role of the amygdala in processing facial expressions of fear is well established, its role in the processing of other emotions, such as sadness, remains unclear. We hypothesized that the amygdala would respond to a negative emotion such as sadness, when sadness was represented by a theatrical mask. In the traditional Japanese Noh theater, performers use masks to indicate many of the mental states of the characters they portray. Here, we report a functional MRI study, in which participants' brains were scanned while viewing Noh masks, whose faces appeared delicately sad. Among seventy standard Noh masks previously rated by the individual participants, we chose six top-rated sad masks and six neutral masks to study the neural correlates of such delicate sadness. Results based on a region of interest analysis indicated the activation of the right amygdala while viewing sad masks. We suggest the fact that such delicate sad masks could activate the amygdala, and it could possibly be because of an underlying similarity to emotions such as fear and disgust.