In this study, associations between alexithymia, interpersonal problems, and cognitive-structural aspects of internal interpersonal representations were examined. Alexithymia was measured using the Toronto Structured Interview for Alexithymia (TSIA) and the 20-item Toronto Alexithymia Scale (TAS-20). To measure interpersonal problems, the dominance and affiliation dimension scores of the Inventory of Interpersonal Problems were used, and cognitive-structural characteristics of interpersonal representations were measured using the Social Cognition and Object Relations Scale (SCORS). As hypothesized, alexithymia was related to cold and withdrawn, but not to dominant or submissive, interpersonal functioning. In terms of the SCORS, alexithymia was negatively related to complexity of interpersonal representations, both in TAT and in interview narratives, indicating a link between alexithymia and mentalization. However, alexithymia was related only to the dimension of social causality when this dimension was scored on TAT narratives. Overall, the TSIA provides the most consistent and stable results after controlling for negative affectivity.