Background: Fetal macrosomia defined as birth weight of 4000 g and above regardless of gestational age and associated with adverse maternal and fetal outcomes, especially among women in developing countries like Ethiopia. Despite the observed burden, there is limited evidence on determinants of fetal macrosomia. This study aimed to identify determinants of fetal macrosomia among live births at Wolaita Sodo town Southern Ethiopia. Methods: A facility-based matched case–control study design involved 360 singletons deliveries attended at hospitals in Wolaita Sodo town, southern Ethiopia, with 120 cases and 240 controls included. Cases and control were matched by maternal age. Cases were neonates with a birth weight of ≥ 4000, while controls were neonates with a birthweight between 2500gm and less than 4000gm. Data were collected by interviews, measuring, and reviewing mothers' medical documents. Conditional logistic regression analysis was carried to identify the independent predictor variables. Statistical significance was set using a p-value < 0.05 and 95% CI for AOR. Results: Male neonates were four times more likely to be macrosomia than female neonates MAOR = 4.0 [95%CI; 2.25–7.11, p < 0.001]. Neonates born at gestational age ≥ 40 weeks were 4.33 times more likely to be macrosomia with MAOR = 4.33 [95%CI; 2.37–7.91, p < 0.001]. Neonates born from physically inactive mothers were 7.76 times more likely to be macrosomia with MAOR = 7.76 [95CI; 3.33–18.08, p < 0.001]. Neonates born from mothers who consumed fruits and dairy products in their diet frequently were 2 and 4.9 times more likely to be macrosomia MAOR = 2.03 [95%CI; 1.11–3.69, p = 0.021] and AOR = 4.91[95%CI; 2.36–10.23, p < 0.001] respectively. Conclusion: Mothers' physical exercise and consumption of fruit and dairy products were significant predictor variables for fetal macrosomia. Hence, health care providers may use these factors as a screening tool for the prediction, early diagnosis, and timely intervention of fetal macrosomia and its complications.