Background: In many urban and peri-urban settings, access to safe drinking water continues to be a major public health issue. Although infrastructure has improved, the association of multidimensional household water access and clinical gastrointestinal (GI) morbidity is incompletely described for hospital-based populations. We sought to examine the relationships of household drinking water access across dimensions with GI morbidity among patients and their caregivers in tertiary hospitals in Dhaka, Bangladesh. Methods: A hospital-based, analytical cross-sectional observational study was carried out from July to December 2025 in two tertiary-care centers. The sample of 150 patients were recruited by consecutive sampling. Data was obtained through face-to-face interviews with a structured questionnaire which included collection of socio-demographics, methods of access to household water (source, treatment, availability and perceived quality), GI morbidity in the past six months. Independent predictors of GI morbidity were determined by multivariable logistic regression. Results: The prevalence of household GI morbidity was 72.0%. Strong bivariate predictors of GI illness included, unimproved water source (90.5% vs. 58.6% for improved sources, p<0.001), no water treatment (94.4% vs. 59.4% for treated water, p<0.001), access <12 hours/day (78.3% vs 66.7%, p=0.035) and belief that there are problems with perceived quality of drinking water (85.3 % VS.43.8 %, P< 0.001). In multivariate analysis, not practicing household water treatment was the most significant independent risk factor (aOR=8.45; 95% CI: 2.68-26.68). Additional strong predictors were perceived water quality problems (aOR=6.03), use of unimproved water sources (aOR=2.91) and access <12 hours/day (aOR=1.72). Conclusion: This study exhibits a robust, independent relationship between unimproved household water access, and in particular lack of point-of-use treatment with GI morbidity. The results point to a dual approach for public health: widespread household water treatment should be promoted as an immediate measure; and also, parallel investment in reliable, higher-level source improved infrastructure that can address the burden of waterborne disease in other such urban settings.