(1) Background: Colorado’s (CO) Environmental Justice mapping tool, CO EnviroScreen, quantifies environmental injustices through “EnviroScreen Scores”, highlighting areas likely affected by environmental health disparities. Identifying the specific scores most strongly associated with mortality could help prioritize interventions and allocate resources to address these issues. This study contributes to sustainable development goals by examining the relationship between environmental justice indicators and population health outcomes. By utilizing the CO EnviroScreen tool, we assess how cumulative environmental exposures and vulnerabilities impact mortality rates, providing insights for sustainable planning and public health policies. (2) Methods: We assessed the cross-sectional association between county-level all-cause mortality rates in CO, using 2019 data from the Colorado Department of Public Health and Environment, and three county-level component scores obtained from CO EnviroScreen: sensitive populations (i.e., health-related outcomes), environmental exposures (e.g., from air, water, noise), and climate vulnerability (i.e., risk of drought, flood, extreme heat, wildfire). A quasi-Poisson generalized linear model was utilized, incorporating covariates (county-level metrics for insufficient sleep, alcohol overconsumption, physical inactivity, and smoking) to explore associations adjusted for behavioral risk factors (n = 64 counties). (3) Results: The analysis revealed that a 10% increase in the “Environmental Exposures” component score was associated with a 3% higher all-cause mortality rate (95% CI: 1.00, 1.05), highlighting the importance of addressing environmental determinants for sustainable community health. No significant associations were observed for the “Sensitive Populations” or “Climate Vulnerability” component scores. (4) Conclusions: This study provides novel evidence of an association between the CO EnviroScreen score, particularly the environmental exposure component, and all-cause mortality rates at the county level in Colorado in 2019. The findings suggest that cumulative environmental exposures may contribute to geographic disparities in mortality risk, even after adjusting for key behavioral risk factors. These results underscore the importance of integrating environmental justice considerations into sustainable development strategies to promote equitable health outcomes and resilient communities. While our study demonstrates the utility of CO EnviroScreen in identifying areas at risk due to environmental factors, it does not establish a direct link to broader environmental justice outcomes. Further research is needed to explore specific environmental exposures and their direct impacts on health disparities to provide a more complete picture of environmental justice in Colorado.