Business sustainability remains a persistent challenge for Small and Medium Enterprises (SMEs) in rural Uganda. This study investigated the distinct impact of three digital payment constructs mobile money adoption, transaction security & trust, and payment system integration on corresponding dimensions of SME sustainability: financial, operational, and market & customer sustainability. A cross-sectional survey design was employed, collecting primary data from a stratified random sample of 178 SME owners/managers in Kasese District between March and May 2025. Data were analysed using descriptive statistics, Pearson correlation, and simple linear regression in SPSS. Results revealed significant positive relationships for all hypothesized paths: mobile money adoption predicted financial sustainability (β = .702, p < .001, R² = .493), transaction security & trust predicted operational sustainability (β = .743, p < .001, R² = .552), and payment system integration predicted market & customer sustainability (β = .721, p < .001, R² = .520). The study concluded that digital payment adoption is a multidimensional driver of SME resilience and recommended integrated, construct-specific interventions to enhance digital financial inclusion and business viability.