Objective In this study, it is aimed to investigate the relationship between the oxytocin level and the rejection sensitivity, childhood mental traumas, and attachment styles in patients diagnosed with borderline personality disorder (BPD). Methods Participants between the ages of 18–30 were included in the study. The patient group consists of 31 participants and the healthy control group consists of 31 participants. Sociodemographic/Clinical Variables Questionnaire, Relationship Scales Questionnaire, Rejection Sensitivity Questionnaire and Childhood Trauma Questionnaire were administered to the participants included in the study. Serum oxytocin levels of the participants were measured using the Elisa method. Results The oxytocin levels were found to be significantly lower in patients with BPD than in healthy control subjects, whereas the rejection sensitivity and childhood traumas were found to be significantly higher. No difference was found between the patient and control groups in terms of attachment styles, yet it was determined that there may be differences between the oxytocin levels of the BPD patients according to the attachment styles the patients have. Conclusion In conclusion, the findings of this study revealed that the rejection sensitivity in BPD patients is not associated with oxytocin levels and childhood traumas, indicating the need to assess the BPD patients in terms of other biopsychosocial factors related to the etiopathogenesis of BPD.