A growing body of research has identified food insecurity as a barrier to antiretroviral therapy (ART) adherence. We systematically reviewed and summarized the quantitative literature on food insecurity or food assistance and ART adherence. We identified nineteen analyses from eighteen distinct studies examining food insecurity and ART adherence. Of the thirteen studies that presented an adjusted effect estimate for the relationship between food insecurity and ART adherence, nine found a statistically significant association between food insecurity and sub-optimal ART adherence. Four studies examined the association between food assistance and ART adherence, and three found that ART adherence was significantly better among food assistance recipients than non-recipients. Across diverse populations, food insecurity is an important barrier to ART adherence, and food assistance appears to be a promising intervention strategy to improve ART adherence among persons living with HIV. Additional research is needed to determine the effectiveness and cost-effectiveness of food assistance in improving ART adherence and other clinical outcomes among people living with HIV in the era of widespread and long-term treatment.