Background: Carers experience significant physical and psychological burden and are at increased risk of experiencing clinical depression. Although several psychological treatments have been shown to be effective for preventing and treating depression in carers, most are complex, costly, and not easily accessible to family carers. In this paper, we review evidence of effectiveness of Behavioural Activation (BA) for depressive symptoms in informal caregivers and report on its quality. Methods: We searched MEDLINE, EMBASE, PsycINFO, CINAHL, CENTRAL and Online trial registers for randomised controlled clinical trials of BA for carers. Results: Twelve trials met inclusion criteria and eleven were included in the meta-analyses. BA reduced depressive symptoms for carers (standardised mean difference (SMD) -0.68; confidence interval (CI) -1.14 to -0.22) at post intervention (4-14 weeks) and in the long term (l year; SMD -0.99; CI -1.26 to -0.71). BA decreased risk of a diagnosis of major depression (Odds Ratio 0.35; CI 0.19 to 0.67), and reduced negative affect (SMD -0.53; 95% CI -0.83 to -0.23), and caregiver burden (SMD -0.32; CI -0.55 to -0.09) at post-treatment. Quality of evidence was moderate and there was no evidence of publication bias. Limitations: There was high heterogeneity in the studies included. Conclusion: BA is effective in reducing depressive symptoms post-treatment and long-term (1 year) and decreases odds of a diagnosis of major depression in informal caregivers. Our review provides further evidence that BA is an effective psychological intervention, which is potentially highly scalable across many settings, populations and cultures (Registration: PROSPERO-CRD42019138860).