Background Identifying environmental factors that influence health in children are necessary to develop preventive strategies. Objective To determine the association between the lifestyles of children (i.e., Mediterranean diet (MD), physical activity (PA), fitness and screen time (ST) with abdominal obesity (AO) of preschoolers from three Spanish-speaking countries (Chile, Colombia and Spain) with different socioeconomic levels and Human Development Index (HDI) indicators. Material and Methods This cross-sectional study included 982 schoolchildren (aged 4-6 years; 56.8% girls) from Chile (n = 409), Colombia (n = 281), and Spain (n = 292). Body mass index (BMI), waist circumference (WC), waist-to-height ratio (WtHR), adherence to the MD, PA, ST and physical fitness were evaluated. Results Spanish preschoolers reported a lower WtHR (p < 0.001), greater physical fitness (Z-score) (p < 0.001) and higher adherence to the MD (p < 0.001) than their Chilean and Colombian peers. In addition, Colombian preschoolers had a better lifestyle (PA + ST) than their Chilean and Spanish peers (p < 0.001). Chilean preschoolers reported a higher prevalence of AO than the Spanish preschoolers (65% vs. 51.9%; p = 0.001). Conclusion Lifestyle had a significant association with AO among Spanish-speaking preschool children, with physical fitness especially being a relevant factor regardless of the country of origin. The findings of the current study may support the development of public guidelines focusing on healthy lifestyles in children to create effective plans that contribute to the early treatment of AO in preschool children.