Alexithymia and autism are variably characterized by social cognitive and perceptual deficits, which can lead to profound social interaction difficulties. Such difficulties are also the hallmark of personality disorders (PDs), but the potential link between alexithymia, autism, and PDs remains unclear. Here, we investigated whether autistic and/or alexithymic traits are associated with specific PD dimensions as measured by the Assessment of Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) Personality Disorders Questionnaire (ADP-IV). We included individuals with a formal autism diagnosis (AP, n = 89), individuals with a psychiatric diagnosis other than autism (NAP, n = 51), and neurotypical participants (NPs, n = 84). We applied linear regression analyses with autistic and alexithymic traits as predictors and PD dimensions as outcome variables, while controlling for age, depressive, and socially anxious symptoms. While autistic traits predicted the obsessive-compulsive PD dimension, alexithymic traits predicted the borderline PD dimension. Autistic and alexithymic traits were both significant predictors of the schizoid PD dimension. Taken together, our results point toward overlaps between autistic traits and specific PD dimensions that are well recognized as differential diagnoses of autism, while alexithymia was differentially linked to the borderline PD dimension.