This study was conducted to investigate the association of eating away from home (EAFH) frequency with hypertension and to explore whether the association was mediated by BMI. A total of 29,611 participants were selected from the Henan Rural Cohort Study. Data on the frequency of EAFH were obtained by face-to-face questionnaires. The relationship between EAFH frequency and blood pressure was evaluated by linear regression. Logistic regression and restricted cubic spline were used to assess the association between EAFH frequency and hypertension, and the mediation effect of BMI on the relationship was performed. There were pronounced associations between the frequency of EAFH and blood pressure (P trend < 0.001) in the total population and men. Compared with the population with 0 times EAFH per week, the multivariate odds ratios (ORs) and 95% confidence intervals (95% CIs) for hypertension of the group with 7 times or more EAFH per week were 1.673 (1.482–1.889) for the total population and 1.634 (1.413–1.890) for men. A nonlinear dose-response relationship was detected between the frequency of EAFH and hypertension (p < 0.001), and the relationship was partially mediated by BMI. The proportion explained was 21.3% in the total population and 25.4% in men. The current study indicated that EAFH was associated with rising blood pressure and increased risk of hypertension and BMI partially mediated the relationship.