Depression is common in primary care, and most patients prefer psychological treatment over pharmacotherapy. Cognitive behaviour therapy (CBT) is an effective treatment, but there are gaps in current knowledge about CBT in the primary care context, especially with regard to long-term effects and the efficacy of specific delivery formats. This is an obstacle to the integration of primary care and specialist psychiatry. We conducted a systematic review and meta-analysis of randomised controlled trials of CBT for primary care patients with depression to investigate the effect of CBT for patients with depression in primary care. A total of 34 studies, with 2543 patients in CBT and 2815 patients in control conditions, were included. CBT was more effective than the control conditions [g = 0.22 (95% confidence interval (CI) 0.15–0.30)], and the effect was sustained at follow-up [g = 0.17 (95% CI 0.10–0.24)]. CBT also led to a higher response rate [odds ratio (OR) = 2.47 (95% CI 1.60–3.80)] and remission rate [OR = 1.56 (95% CI 1.15–2.14)] than the control conditions. Heterogeneity was moderate. The controlled effect of CBT was significant regardless of whether patients met diagnostic criteria for depression, scored above a validated cut-off for depression, or merely had depressive symptoms. CBT also had a controlled effect regardless of whether the treatment was delivered as individual therapy, group therapy or therapist-guided self-help. We conclude that CBT appears to be effective for patients with depression in primary care, and recommend that patients with mild to moderate depression be offered CBT in primary care.