Background: Poor diet and sleep are risk factors for hypertension, the initiation and progression of which are closely associated with inflammation. Objective: We aim to explore how the dietary inflammatory index (DII) scores and sleep duration are associated with the prevalence of hypertension and prehypertension across the American population. Methods: Data were obtained on 10,052 adult participants in the 2017–2023 National Health and Nutrition Examination Survey (NHANES). To explore the correlations among hypertension, pre-hypertension, dietary inflammatory index (DII), and sleep duration, we employed binary logistic regression analysis and conducted subgroup analyses stratified by gender using the Cox proportional hazards regression model. In addition, we employed RCS regression analysis to further examine the association between DII scores combined with parameters related to obesity and hypertension as well as pre-hypertension. Mediation analysis was employed to evaluate the potential mediating effects of key variables in these relationships. Results: The lowest DII quartile (Q1) was used as the reference, and the top quartile (Q4) was discovered to be associated with an increased risk of hypertension (OR = 1.30, 95% Cl = 1.04–1.63). Normal sleep duration reduced hypertension risk (OR=0.81, 95% CI:0.67–0.98) versus short sleep. Subgroup analysis revealed higher hypertension risk in older men (HR=1.112, 95% CI:1.041–1.187) and younger women (HR=1.217, 95% CI:1.075–1.379). RCS curve analysis demonstrated a nonlinear relationship between DII scores, obesity-related factors, and hypertension for both men and women (ptotal < 0.001, pnonlinear < 0.001). Mediation analysis identified glycated hemoglobin and smoking as partial mediators. Conclusions: DII scores are strongly associated with hypertension and prehypertension in the American population. Normal sleep duration and an anti inflammatory diet may reduce the likelihood of hypertension in adults.