Background Beta-thalassemia major patients are at increased risk of complications including endocrinopathies and bone disease due to iron overload. So, this study aimed to assess the growth parameters, serum levels of 25-OH-vitamin D, calcium, and phosphorous in children with beta-thalassemia major. This was a case-control study that included 55 children with beta-thalassemia major compared with 30 sex- and age-matched healthy children that served as a control group. All enrolled children were subjected to full history taking, clinical examination including anthropometric measurements, and laboratory investigations including complete blood count, serum ferritin, levels of serum calcium, phosphorus, and 25-OH-vitamin D. Results Body mass index was statistically significantly lower in the thalassemic group (P < 0.001). It was observed that vitamin D levels were significantly lower in thalassemic patients than in controls (P value < .0001). The mean serum 25-OH-vitamin D levels were 19.84 ± 5.79 ng/ml and 44.98 ± 5.77 ng/ml, respectively; 22 cases (40%) had insufficient vitamin D, and 5 cases (9%) had deficient vitamin D. Regarding serum calcium and phosphorous, there was no significant difference between the thalassemic and control groups. Conclusion Children with beta-thalassemia major had low body mass index and metabolic abnormality in the form of lower serum levels of vitamin D that signify the importance of therapeutic interventions.