BACKGROUND: There is debate on the link between dietary fiber intake and stroke risk. The purpose of this study was to look at how it impacts dietary fiber intake and stroke risk, as well as mortality among stroke survivors. Two-sample Mendelian randomization was also used to investigate the causal relationship. METHODS: This research examined information from 1453 patients with stroke participating in the National Health and Nutrition Examination Survey from 1999 to 2018. To assess the incidence of stroke, we conducted a survey-weighted multivariate logistic regression analysis and subgroup analysis. To evaluate the mortality associated with stroke, we used Kaplan-Meier survival analysis combined with survey-weighted Cox regression models. Using 2-sample Mendelian randomization and inverse-variance weighted method, we established a causal relationship between dietary fiber intake and stroke. The article was organized according to Strengthening the Reporting of Observational Studies in Epidemiology and Strengthening the Reporting of Observational Studies in Epidemiology Using Mendelian Randomization guidelines. RESULTS: In the fully adjusted model, dietary fiber intake was negatively associated with stroke (odds ratio, 0.98 [95% CI, 0.97–0.99]; P <0.0001; T3 versus T1; odds ratio, 0.71 [95% CI, 0.57–0.88]; P =0.002). A stable linear negative relevance was confirmed between dietary fiber intake and stroke risk (nonlinear P =0.566) by the multivariate adjusted spline regression model. According to the survey-weighted multivariate Cox regression model, dietary fiber intake significantly reduced all-cause mortality (T3 versus T1; odds ratio, 0.68 [95% CI, 0.47–0.97]; P =0.04). Further Kaplan-Meier survival analysis indicated that higher intake of dietary fiber improved the survival of patients with stroke ( P =0.02325). The 2-sample Mendelian randomization analysis showed that genetic prediction supported a causal relationship between increased dietary fiber intake and reduced risk of small vessel stroke (odds ratio, 0.8326 [95% CI, 0.7051–0.9833]; P =0.0309). CONCLUSIONS: There is a stable negative correlation between dietary fiber intake and stroke risk. High fiber intake is associated with reduced all-cause mortality among stroke survivors. Additionally, genetic prediction further demonstrates a causal relationship between dietary fiber and reduced risk of small vessel stroke.