Background: Eyelash extensions involve the attachment of synthetic eyelashes made of chemical fibers or other materials individually onto natural lashes. However, there are no uniform or well-established guidelines for this procedure. Consultations with ophthalmologists and local consumer centers regarding eyelash-extension-related skin and eye disorders have been increasing yearly throughout Japan. This study was conducted to obtain epidemiologic data on eyelash extensions and their related health problems among the Japanese. Methods: A web-based survey was prepared and conducted with questions regarding the basic characteristics of the study participants, their experience with eyelash extensions (including the number of procedures, frequency of extension, year of first extension, and years since the first extension), and any extension-related health problems. Data from 2000 women, aged 15 to 59 years and randomly selected from across the country in accordance with the demographic composition of Japan, were included in the analysis. Results: In total, 205 (10.3%) respondents reported having experienced eyelash extensions (average, 6.2 procedures; median, 3.0), with a peak among those aged 25 to 29 years and a larger proportion of those living in urban areas than in rural areas. Of these women, 55 (26.8%) experienced health problems such as ocular hyperemia, pain, and itchy swollen eyelids. Multivariate analysis revealed that short intervals of extensions were associated with health problems (multiadjusted odds ratio (95% confidence interval); 2.88 (1.09–7.61)). Conclusions: Eyelash extensions are a popular procedure, especially among urban, young women. However, attention must be paid to the potential health risks of the procedure.