The present study investigated the relationship between adult attachment and depression and the moderating effects of social support in secondary school teachers. Survey data was collected from 231 secondary school teachers working at three middle and high schools in the Seoul and Gyung-gi areas. Correlation and hierarchical multiple regression analyses were used to test the relationships among the main variables, namely adult attachment, social support, and depression, and the three moderating effects of social support in the relationship between adult attachment and depression, respectively. The main results were as follows. First, each sub-dimension of adult attachment, namely dependent attachment, anxiety attachment, and close attachment, were significantly correlated with depression levels. All of the variables except senior support and dependent attachment were significantly correlated with depression. Second, social support had a moderating effect in the relationship between anxiety attachment and depression. Colleague and family support had moderating effects in the relationship between dependent attachment and depression though senior support did not.