Small and Medium Enterprises (SMEs) in rural Uganda faced significant sustainability challenges. While digital adoption is promoted as a solution, empirical evidence on which specific digital practices most strongly predict sustainability outcomes in contexts like Kasese District is scarce. This study employed a descriptive and correlational cross-sectional survey design. Data were collected from 151 SME owners/managers in Kasese District (93% response rate) using a structured questionnaire with 5-point Likert scales. Analysis using SPSS version 26 involved descriptive statistics, Pearson correlation, and simple linear regression to test the hypothesis. Online Customer Engagement (CE) demonstrated a very strong, significant positive correlation with Business Sustainability (BS) (r = .784, p < .01). The regression model was statistically significant, F(1, 149) = 177.156, p < .001, explaining 61.4% of the variance in BS (R² = .614). The unstandardized coefficient (B = 0.812) indicates that for every one-unit increase in CE, BS increases by 0.812 units. The standardized coefficient (Beta, β = .784) confirms a strong positive effect. Online Customer Engagement is the most potent predictor of business sustainability among the digital practices examined. The study concludes that for SMEs in developing regions, strategic investment in interactive, responsive, and feedback-driven digital engagement is critical for achieving long-term viability, customer retention, and competitive resilience. Recommendations for SME owners and policymakers are centered on building digital engagement capacity.