This study investigated the impact of family background on students' academic performance in selected secondary schools in Kakumiro District, with a focus on St. Joseph S.S. Nkooko. Academic underperformance among secondary school students remains a persistent concern in rural Ugandan districts, and family background factors, including parental education, socio-economic status, and family structure, have been implicated as key determinants. The study was guided by three objectives: to examine the influence of parental education level on students' academic performance, to assess the effect of family socio-economic status on academic performance, and to establish the relationship between family structure and students' academic performance. A descriptive correlational research design was employed, targeting a population of 310 Senior Four students, from which a sample of 175 students was selected using Krejcie and Morgan's (1970) table and stratified random sampling. A structured questionnaire was used to collect data on family background variables, while students' end-of-term aggregate scores were used as a proxy for academic performance. Data were analysed using SPSS version 26 employing descriptive statistics, Pearson correlation, and multiple linear regression. The findings revealed that parental education (r = 0.487, p < 0.01) and family socio-economic status (r = 0.541, p < 0.01) were significantly and positively correlated with academic performance, while family structure showed a weaker but still significant correlation (r = 0.298, p < 0.01). The regression model showed that the three family background factors jointly explained 41.2% of the variance in academic performance (R² = 0.412, F(3,171) = 39.87, p < 0.001), with socioeconomic status emerging as the strongest predictor (β = 0.372, p < 0.001). The study concludes that family background significantly shapes students' academic performance and recommends targeted interventions, including bursary schemes and parental sensitisation programmes, to mitigate the effects of disadvantaged family backgrounds.