Hypertension is a leading risk factor for increased mortality and morbidity. One pathogenesis mechanism, increased peripheral vascular resistance, relates to arteriolar diameter. Retinal arterioles, visualized and measured through retinal images, provide an insight into the microvascular structure and hints of peripheral vascular resistance. Multiple studies have demonstrated an inverse association between increasing blood pressure and narrowing retinal arteriolar diameter. This systematic review summarizes the currently available evidence from cross-sectional and longitudinal population-based studies that have investigated this association. A meta-analysis of five cross-sectional studies (19,633 adults) provided an averaged regression coefficient of -3.07 μm (95% CI, -3.73, -2.40) narrowing in retinal arteriolar diameter for every 10 mm Hg increase in mean arterial blood pressure. Four longitudinal studies (6,247 adults) with follow-up periods ranging from 3 to 7 years consistently showed that generalized retinal arteriolar narrowing (defined as the lowest tertile, quartile, or quintile in the population) was associated with an increased risk of incident hypertension (meta-analysis odds ratio 1.91; 95% CI, 1.56-2.34).