Background A recently updated Cochrane review supports the efficacy of psychotherapy for borderline personality disorder (BPD). Aims To evaluate the effects of standalone and add-on psychotherapeutic treatments more concisely. Method We applied the same methods as the 2020 Cochrane review, but focused on adult samples and comparisons of active treatments and unspecific control conditions. Standalone treatments (i.e. necessarily including individual psychotherapy as either the sole or one of several treatment components) and add-on interventions (i.e. complementing any ongoing individual BPD treatment) were analysed separately. Primary outcomes were BPD severity, self-harm, suicide-related outcomes and psychosocial functioning. Secondary outcomes were remaining BPD diagnostic criteria, depression and attrition. Results Thirty-one randomised controlled trials totalling 1870 participants were identified. Among standalone treatments, statistically significant effects of low overall certainty were observed for dialectical behaviour therapy (self-harm: standardised mean difference (SMD)-0.54, P = 0.006; psychosocial functioning: SMD-0.51, P = 0.01) and mentalisation-based treatment (self-harm: risk ratio 0.51, P < 0.0007; suicide-related outcomes: risk ratio 0.10, P < 0.0001). For adjunctive interventions, moderate-quality evidence of beneficial effects was observed for DBT skills training (BPD severity: SMD-0.66, P = 0.002; psychosocial functioning: SMD-0.45, P = 0.002), and statistically significant low-certainty evidence was observed for the emotion regulation group (BPD severity: mean difference-8.49, P < 0.00001), manual-Assisted cognitive therapy (self-harm: mean difference-3.03, P = 0.03; suicide-related outcomes: SMD-0.96, P = 0.005) and the systems training for emotional predictability and problem-solving (BPD severity: SMD-0.48, P = 0.002). Conclusions There is reasonable evidence to conclude that psychotherapeutic interventions are helpful for individuals with BPD. Replication studies are needed to enhance the certainty of findings.