PURPOSE: To describe the ethnic variations in the prevalence and risk factors for undercorrected refractive error and its impact on vision-specific functioning (VF) in a multiethnic Asian population. METHODS: A total of 3353 Chinese, 3400 Indians, and 3280 Malays in Singapore participated in this population-based cross-sectional study. Distance presenting visual acuity (VA) was measured using a logarithm of the minimum angle of resolution number chart. Best-corrected VA was assessed using the same test protocol as presenting VA. Undercorrected refractive error was defined as an improvement of at least 0.2 logarithm of the minimum angle of resolution (two lines equivalent) in the best-corrected VA compared with the presenting VA in the better eye when presenting VA was less than 20/40 in the better eye. The VF-11 questionnaire measured participants' VF. Multivariate linear regression was performed to assess the impact of undercorrected refractive error on the overall VF score. RESULTS: Regardless of ethnicity, participants with undercorrected refractive error had a reduction in VF score compared to those with normal vision in both eyes. The overall prevalence of undercorrected refractive error was highest in Indians (25.1%), followed by Malays (22.2%) and Chinese (19.7%). Undercorrected refractive error was less common in spectacles or contact lenses wearers than in non-spectacle wearers or non-contact lenses wearers. Adults with mild to moderate refractive errors were most likely to have undercorrected refractive error (p < 0.001). In multivariate analysis, increasing age (p < 0.001), Indian race (p < 0.001), lower education level (p < 0.001) or poorer housing (p < 0.001), having refractive errors (p < 0.001), and not wearing optical corrections (p < 0.001) were significantly associated with increasing undercorrected refractive error. CONCLUSIONS: In Singapore, undercorrected refractive error is most prevalent in Indians and least prevalent in Chinese. The impact of undercorrected refractive error on VF was consistent across all three ethnicities. There may be higher barriers to visual correction among Malays or Indians compared with Chinese in Singapore.