Increasing digitization also raises concerns regarding the reliability and comprehensibility of online health information. In this study, we aimed to examine the readability, reliability, and quality of internet-based patient education materials on "transcutaneous electrical nerve stimulation." On September 15, 2022, we used Google search engine to search the keyword "Transcutaneous Electrical Nerve Stimulation" and obtained information from 200 websites. The readability of the websites was evaluated using the Flesch Reading Ease Score (FRES), Flesch-Kincaid Grade Level, Simple Measure of Gobbledygook, and Gunning Fog. The Journal of American Medical Association score and Health on the Net Foundation code of conduct were used to determine the reliability of the websites, whereas the DISCERN score and Global Quality Score were used to evaluate the quality of the websites. In the readability analysis of 102 websites that met the inclusion criteria of this study, we found that the Flesch Reading Ease Score was 47.91 ± 13.79 (difficult), average Flesch-Kincaid Grade Level and Simple Measure of Gobbledygook were 11.20 ± 2.85 and 10.53 ± 2.11 years, respectively, and average Gunning Fog score was 14.04 ± 2.74 (very difficult). Commercial websites constituted the highest proportion of websites (n = 36, 35.5%). Overall, 16.7% of the websites were found to be of high quality according to the Global Quality Score, 16 (15.7%) websites had Health on the Net Foundation code of conduct certification, and 8.8% of the websites were found to be highly reliable according to the Journal of American Medical Association scores. There was a statistically significant difference between website typologies and quality and reliability scores (P < .001). Compared with the sixth-grade level recommended by the American Medical Association and the National Institute of Health, the readability of transcutaneous electrical nerve stimulation-related internet-based patient education materials was considerably high, but they showed low reliability and moderate-to-poor quality. Thus, the quality, reliability, and readability of websites developed by health professionals play a major role in conveying accurate and easily understandable information.