Monitoring anthropometry, dietary intake, and physical activity (PA) is essential to prevent/counteract childhood obesity. This study examined dietary intake, PA, and anthropometric characteristics in young boys practicing soccer as a recreational sport. A cross-sectional study included 226 boys aged 8 to 13 years participating in soccer as a recreational activity in football academies located in Tunis, Tunisia. Anthropometric measures allowed the calculation of body mass index, fat mass, and peak height velocity as markers of biological maturity. A three-day food record and a food frequency questionnaire estimated nutrient intake and eating habits. The International Physical Activity Questionnaire (IPAQ) was used to estimate the PA level of the participants. It was found that a high percentage of the children had excess weight (54%) and excess fat mass (47%). The total energy, carbohydrate, and saturated fat intake of the children exceeded the recommended levels by approximately 10%, 15%, and 30%, respectively. However, the intake of unsaturated fat was below the estimated requirements, particularly in obese children. In addition to the unbalanced macronutrient intake, the children also showed an insufficient intake of many essential micronutrients. Around 60% to 70% of the children in all three groups had a low intake of magnesium, n-3 polyunsaturated fatty acids (PUFA), and vitamins B9, B12, and D. Moreover, 20% to 35% of the children in the three groups had an insufficient intake of vitamins A and C. Insufficient vitamin E intake was found in 63% of obese children and 35% of non-obese children. It was observed that the PA level was lower in the overweight/obese group compared to the normal-weight group (p < 0.005). More than three-quarters of overweight/obese children had low PA levels, about 20% were moderately active, and only 1 to 2% were highly active. Conversely, normal-weight children showed moderate to high PA levels. Poor eating behavior, an unbalanced diet, and a low PA level are prevalent in Tunisian boys practicing recreational sports. Such a combination is responsible for a disparity between energy intake and expenditure, contributing to weight excess and increased cardiometabolic risk. The study findings provide meaningful information for practitioners and authorities on applying a balanced diet and adequate PA to prevent and fight against obesity and improve cardiometabolic health in youth.