We investigated the associations between depressive symptoms and adherence to antiretroviral therapy (ART) among people living with HIV (PLHIV). We searched the PubMed, EMBASE and Cochrane CENTRAL databases for studies that reported an association between depression and adherence to ART as a primary or secondary outcome. We used a random-effect model to pool the risk estimates from the individual studies. The odds ratio (OR) with their 95 % CIs were used as summary estimates. Of 2861 citations, 111 studies that recruited 42,366 PLHIV met our inclusion criteria. When reported, the rate of PLHIV with depressive symptoms ranged from 12.8 to 78 % and the proportion of PLHIV who achieved good adherence (≥ 80 %) ranged from 20 to 98 %. There were no significant differences in rate of depressive symptoms in PLHIV by country income group; however, the proportion of PLHIV who achieved good adherence was significantly higher in lower-income countries (as defined in the 2012 World Bank Country Income Groups) (pooled rate=86 %) compared to higher-income countries (pooled rate=67.5 %; p< .05). We found that the likelihood of achieving good ART adherence was 42 % lower among those with depressive symptoms compared to those without (pooled OR=0.58, 95 % CI 0.55 to 0.62). The relationship between depressive symptoms and adherence to ART was consistent across the country's income group, study design and adherence rates. We found that the magnitude of the association significantly decreases with more recent publications and increasing study sample size. The higher the prevalence of depressive symptoms of PLHIV recruited in the studies, the lower the likelihood of achieving good adherence to ART. In conclusion, the likelihood of achieving good adherence was lower among those with depressive symptoms compared to those without.