INTRODUCTION: Considering the scarcity of information on the assessment of chronic diseases in traditional Amazonian populations, as well as public health policies focused on their specificities, this study aimed to estimate the prevalence of at least one of the chronic diseases (systemic arterial hypertension (SAH) or diabetes mellitus (DM)) and their concomitant occurrence in a rural riverside population of the Amazon, and determine the associated factors. METHODS: A household-based cross-sectional survey was conducted with a sample of adults and elderly people living in rural riverside locations along the left bank of the Negro River, in the municipality of Manaus, Amazonas, Brazil. The outcomes evaluated were the presence of at least one of the evaluated chronic diseases and the concomitant occurrence, based on the self-reported medical diagnosis of SAH and DM. Analysis of associated factors (sociodemographic, behavioral, and access to health services variables) was performed by Poisson regression with robust variance. RESULTS: The sample consisted of 495 individuals (young adults (n=257; 51.9%), middle-aged (n=132; 26.7%), and elderly (n=106; 21.4%)), of whom 51.5% were women (n=255), mean age 43.3±17.1 years. The monthly household income was on average R$1100±902 (A$345±283). The diagnosis of any chronic disease was reported by 18.8% of the sample, with a preponderance of SAH (17.4%). The occurrence of at least one of the chronic diseases was associated with higher average age and worse health self-assessment. Regarding concomitant occurrence of SAH and DM, prevalent in 4.4% of the sample, the same associations were observed. CONCLUSION: The data for the occurrence of chronic diseases in the studied Amazon rural riverside populations are worrying, because these people live in areas of socioeconomic vulnerability, with a lack of basic sanitation infrastructure, difficult geographic access, and limited access to health care. Health policies fail to recognize the specificities of these populations, which implies deficiencies in the provision of necessary regular care. The findings also reinforce the need to strengthen health promotion and chronic disease prevention strategies in the context of primary care.