Background Quality of care and access to effective interventions have been widely criticised as limited for people diagnosed with ‘personality disorder’ or who have comparable needs (described in some recent papers as “Complex Emotional Needs” (CEN). It is important to identify effective interventions and the optimal context and mode of delivery for people with CEN. We aimed to investigate the effectiveness of psychosocial interventions delivered in community and outpatient settings in treating symptoms associated with ‘personality disorder’, and the moderating effects of treatment-related variables. Methods We systematically searched MEDLINE, EMBASE, PsycINFO, CINAHL, HMIC, ASSIA for articles published in English, from inception to November 23, 2020. We included randomized controlled trials examining interventions provided in community or outpatient settings for CEN. The primary outcome was ‘personality disorder’ symptoms, while secondary outcomes included anxiety symptoms, depressive symptoms, and global psychiatric symptoms. Random-effects meta-analysis was conducted for each outcome, and meta-regression analysis was performed to assess the moderating effects of treatment characteristics. The quality of the studies and the degree of publication bias was assessed. Results We included 54 trials (n = 3716 participants) in the meta-analysis. We found a large effect size (g = 0.78, 95% CI: 0.56 to 1.01, p < 0.0001) favoring interventions for ‘borderline personality disorder’ (BPD) symptoms over Treatment as Usual or Waitlist (TAU/WL), and the efficacy was maintained at follow-up (g = 1.01, 95% CI: 0.37 to 1.65, p = 0.002). Interventions effectively reduced anxiety symptoms (g = 0.58, 95% CI: 0.21 to 0.95, p = 0.002), depressive symptoms (g = 0.57, 95% CI: 0.32 to 0.83, p < 0.0001), and global psychiatric symptoms (g = 0.50, 95% CI: 0.35 to 0.66, p < 0.0001) compared to TAU/WL. The intervention types were equally effective in treating all symptom categories assessed. Treatment duration and treatment intensity did not moderate the effectiveness of the interventions for any outcome. Conclusions People with a ‘personality disorder’ diagnosis benefited from psychological and psychosocial interventions delivered in community or outpatient settings, with all therapeutic approaches showing similar effectiveness. Mental health services should provide people with CEN with specialised treatments in accordance with the availability and the patients’ preferences.