Background Cognitive impairment (CI) is highly prevalent among older adults with hypertension and imposes substantial burdens on individuals, families, and healthcare systems. Identifying factors associated with CI is essential for developing targeted prevention strategies, yet evidence from tropical regions of China remains limited. Objective To examine the prevalence of CI and factors associated with CI among community-dwelling older adults with hypertension in tropical China. Methods This community-based cross-sectional study included 735 older adults aged ≥60 years with self-reported, physician-diagnosed hypertension recruited from community health centers in Haikou, China, between 2023 and 2025. Cognitive function was assessed using the Chinese Mini-Mental Status with education-adjusted cutoff values. Multivariable logistic regression was performed to identify factors associated with CI. Age- and sex-stratified analyses, interaction analyses, and sensitivity analyses were conducted to evaluate the robustness of the findings. Results Among the 735 participants (mean age, 72.3 ± 7.7 years; 57.6% women), 223 (30.3%) had CI. In the fully adjusted model, participants aged ≥80 years had significantly higher odds of CI than those aged 60–69 years (OR = 2.21, 95% CI: 1.34–3.64). Depressive symptoms were also associated with increased odds of CI (OR = 1.87, 95% CI: 1.03–3.39), whereas higher educational attainment, medium monthly income, and higher BMI were associated with lower odds of CI. Stratified analyses suggested potential sex differences in the association between marital status and CI, and formal interaction analysis demonstrated a significant interaction between sex and marital status (P for interaction = 0.015). Sensitivity analyses generally supported the robustness of the primary findings. Conclusion CI was common among community-dwelling older adults with hypertension in tropical China. Older age and depressive symptoms were associated with higher odds of CI, whereas higher educational attainment, moderate income, and higher BMI were associated with lower odds. The observed sex differences in the association between marital status and CI highlight the importance of considering social determinants and sex-specific approaches when developing community-based cognitive health strategies for older adults with hypertension.