Introduction. Informal Primary Caregivers (IPC) of people with borderline personality disorder (BPD) experience a significant burden, making it important to determine their specific needs. Objectives. Cross-sectional study aimed at adapting and establishing the reliability of the Questionnaire on the Needs of Family Members of People with Severe Mental Disorders to identify felt and unfelt needs that may or may not have been met in IPCs of patients with BPD and suggest intervention strategies to effectively address them. Method. The adapted version of the instrument was completed by 80 IPCs of patients with confirmed BPD diagnosis. Results. Cronbach’s alpha coefficients for different groups of needs evaluated through the instrument were: Knowledge/information = .77, Instrumental support = . 78, Participation = .63, and Personal support = .74; and for the total score = .86. The most important unmet felt needs were: 1. having information on interventions for patients and caregivers, legal and administrative aspects, and available support services; 2. having coping skills to deal with crises and manage patients’ risk behaviors; 3. receiving professional care to reduce stress; and 4. being listened by health professionals, express their personal opinions, and need for rest. Conclusions. The adapted instrument showed satisfactory internal consistency in IPCs of patients with BPD. The results highlight the urgent need for interventions for this population, focusing on psychoeducation, assertiveness training, stress management, and problem solving.