We assessed the impact of diabetes in a large Puerto Rican community of Chicago by measuring the prevalence of diagnosed diabetes and calculating the diabetes mortality rate. Data were analyzed from a comprehensive health survey conducted in randomly selected households in community areas. Questions on diagnosed diabetes and selected risk factors were asked. In addition, vital records data were analyzed in order to calculate the age-adjusted diabetes mortality rate. When possible, rates were compared to those found in other studies. The diabetes prevalence located in this community (20.8%: 95% CI = 10.1%-38.0%) is the highest ever reported for Puerto Ricans and one of the highest ever reported in the United States for a non-Native American population. For instance, it is twice the prevalence for Puerto Ricans in New York (11.3%) and Puerto Rico (9.3%-9.6%). Diagnosed diabetes was found to be significantly associated with obesity (p = 0.023). The prevalence was particularly high among older people, females, those born in the US, and those with a family history of diabetes. Notably, the diabetes mortality rate (67.6 per 100,000 population) was more than twice the rate for all of Chicago (31.2) and the US (25.4). Understanding why the diabetes prevalence and mortality rates for Puerto Ricans in this community are so much higher than those of other communities is imperative for primary and secondary prevention. Collaboration between researchers, service providers and community members can help address the issues of diabetes education, early screening and diagnosis, and effective treatment needed in this community.