ObjectiveWe examined the impact of teleworking frequency, including influencing factors and work functioning impairment.MethodsThis online cross-sectional study was conducted using a self-administered questionnaire among 27,036 full-time Japanese workers. We used the Work Functioning Impairment Scale to measure work functioning impairment and performed multilevel logistic regression analysis.ResultsWe observed higher odds for work functioning impairment among employees who teleworked 4 or more days a week compared with those almost never teleworked: odds ratio (OR) 1.18, 95% confidence interval (CI) 1.07–1.3. After adjusting for influencing factors (teleworking preference, changes in working time, and commuting time), there was no significant association between teleworking frequency and work functioning impairment (OR 0.93, 95% CI 0.82–1.05).ConclusionsFrequent telework may cause work functioning impairment; this can be explained by the impact of influencing factors.