The experiences of stigmatization among people living with specific Serious Mental Illnesses (SMI), such as Borderline Personality Disorder (BPD) has not been addressed by the scientific literature. In this study we wanted to explore how people living with BPD experience stigmatization. We examine the experiences of 8 people (7 women and 1 man) living and receiving treatment for BPD in Puerto Rico. We used an exploratory qualitative design with semi-structured interviews. To interpret our data, we conducted a thematic analysis. We discuss three categories that focus on one identified theme: the interpersonal dimension of the stigmatization process. These categories are (a) society’s views of people living with BPD, (b) family relationships, and (c) partner relationships. Our findings show that people with BPD experience a high attributed personal responsibility, discrimination, social exclusion, and lack of social support. In addition, our findings suggest that the stigmatization of BPD might be more complex than other mental illnesses as it shares characteristics of both SMI and less severe forms of mental illness. We also discuss the importance for practitioners to address stigmatization in therapy and the importance for research to address other aspects of the stigmatization process such as its structural dimension.