Introduction: There is evidence that urban design characteristics, including greater green space provision, have positive effects on health. Possible mechanisms include more opportunity for exercise, better air quality, smaller urban heat island effects, and lowered stress levels. Only a few previous studies have examined associations between green space and mortality and they have given inconsistent results. We conducted an ecological study relating green space to mortality in Hong Kong from 2006-2011. Methods: Normalized Difference Vegetation Index (NDVI), a measure of green space coverage, was measured for 199 small geographic areas in Hong Kong. Negative Binomial Regression Models were fit for each mortality outcome with NDVI as a covariate, and age, gender, population density, and area-level measures of socioeconomic status controlled as confounders, with Generalized Estimating Equations used to control for within-area correlation. Results: There were 236734, 58854, 21422, 11744, and 2964 deaths from all natural causes, cardiovascular diseases (CVD), lung cancer, chronic respiratory diseases (CRD), and diabetes, respectively. An increase of 0.44 units in NDVI, equivalent to it’s observed interquartile range, was significantly associated with lower CVD (relative risk (RR) = 0.88, 95% confidence interval (CI) = 0.80, 0.98) and diabetes (RR = 0.72, 95% CI = 0.60, 0.92) mortality, and marginally significantly associated with lower CRD mortality (RR = 0.90, 95% CI = 0.79, 1.02). These associations were stronger for males and residents of low-income areas. Lung cancer mortality had no significant association with green space. Conclusions: Better provision of green space in urban areas, particularly in low income areas, seems to have potential to reduce mortality in densely populated Asian cities. Policy makers involved in urban planning should consider these findings when making difficult decisions concerning land use in an era of rapid urban population growth.