Purpose <p>Interoception has been reported to be impaired in patients with restrictive eating disorders (REDs), while its role in patients with borderline personality disorder (BPD) is more controversial. We set out to conduct a clinical study to explore the relationship between interoception, eating disorders, and BPD.</p> Methods <p>We recruited a sample of 75 female adolescents affected by REDs, of whom 21 received a diagnosis of comorbid BPD. In addition to collecting demographic and clinical data, we administered measures of interoceptive awareness (MAIA-2), the scale for eating symptomatology (EDI-3), and alexithymia (TAS-20) to all patients.</p> Results <p>Patients with REDs and comorbid BPD reported lower scores on the MAIA-2 Not-Distracting (p = 0.046) and Trusting (p = 0.023) subscales, reflecting decreased focus and reliance on bodily sensations of pain or discomfort compared to patients with REDs only. Lower scores on the MAIA-2 Trusting subscale were associated with higher scores on all EDI-3 subscales and on the total TAS-20 scale (p = 0.005), whereas lower scores on the MAIA-2 Not-Worrying subscale were associated with higher scores on the EDI-3 Interpersonal Problems composite subscale (p = 0.049), and higher scores on the MAIA-2 Noticing subscale were associated with higher scores on the EDI-3 Affective Problems composite subscale (p = 0.003).</p> Conclusions <p>Interoceptive dysfunction appears to be a key vulnerability factor for eating disorder psychopathology in female adolescents with REDs, with comorbid BPD potentially further exacerbating these impairments. Targeting interoceptive processes may represent a promising therapeutic approach to improve emotion regulation and clinical outcomes, particularly in patients with co-occurring BPD, and warrants further investigation in this clinical population.</p> <p><i>Level III</i> Evidence obtained from cohort or case–control analytic studies.</p>