This study investigated the relationship between work-life balance (WLB) and employee performance at Uganda Christian University (UCU), Mukono. A convergent parallel mixed-methods design was employed, utilizing a structured questionnaire administered to a stratified random sample of 150 academic and administrative staff, in-depth interviews with 15 key informants, and analysis of secondary performance data. Quantitative data were analyzed using both SPSS for descriptive statistics, reliability analysis, and bivariate correlations, and STATA for multiple logistic regression to model the predictors of high work-life conflict and high performance. The results revealed that high workload was the most significant predictor of work-life conflict, with affected staff being 3.86 times more likely to experience high conflict. A lack of flexible working hours and technology intrusion were also significant contributing factors, with odds ratios of 2.51 and 2.25, respectively. Academic staff were significantly more vulnerable than their administrative counterparts. Crucially, the regression analysis demonstrated a strong positive relationship between good WLB and performance; staff with good WLB were three times more likely to be high performers. Supervisor support and job autonomy were key facilitators of performance, while high workload had a severe negative impact, reducing the odds of high performance by 57%. The study concluded that work-life imbalance at UCU Mukono, driven primarily by excessive workload, institutional inflexibility, and the "always-on" culture, is a direct and significant determinant of diminished employee performance. This undermines both staff well-being and the university's strategic objectives. It was recommended that the university implement a comprehensive workload management system, formalize flexible work arrangements, establish a "Right to Disconnect" protocol, and enhance supportive leadership training. These actions are essential for translating the university's mission of a "complete person" into tangible human resource practices that secure sustainable institutional performance and employee wellbeing.