Aims: The aim of the study was to assess the incidence of sleep-related breathing disorders (SRBD) in children with Down Syndrome (DS) living at high altitude. Methods: A retrospective descriptive study was conducted on 53 children with DS who underwent polysomnography (PSG) at San Ignacio University Hospital (2640 m/8660 ft above sea level) from 2009 to 2016. Data were extracted from official PSG reports and analyzed using measures of central tendency and dispersion, frequency calculation, ranges, and confidence intervals. Associations were examined using t-test, chi-square test, and analysis of variance test. Results: Obstructive sleep apnea (OSA) was present in 90.5% of children. Central sleep apnea was evident in 11.3%. Periodic breathing was seen in 15.1% of patients. Snoring was able to predict OSA with a sensitivity of 61.7%, a specificity of 100%, and negative predictive value of 25%. Conclusion: Children with DS who live at high altitude have a high incidence of SRBD. Our findings show a higher incidence of SRBD than previously reported in the population with DS. Furthermore, snoring was not sensitive enough to predict OSA. This high risk of SRBD may increase the risk of other comorbid conditions seen in the population with DS. Our results support the need for routine PSG screening independent of symptoms such as snoring status.