Introduction: Vitamin D is crucial for bone growth, mineralization, and various metabolic processes in the body. Consequently, a deficiency or insufficiency of this vitamin can lead to long-term consequences, especially in children. Therefore, this study aimed to assess the prevalence of vitamin D deficiency vitamin D deficiency in children aged between 1 to 16 years. Methods: This was an observational study conducted in the Department of Paediatrics, Dr. Sirajul Islam Medical College & Hospital, Dhaka & Ad-Din Akij Medical College Hospital, Khulna, Bangladesh during the period from July 2023 to July 2024. The study enrolled children aged 1 to 16 years from the pediatric department, excluding those with specific health issues. Data analysis was conducted with SPSS 23, and ethical approval was obtained from Dr. Sirajul Islam Medical College & Hospital and Ad-Din Akij Medical College Hospital. Results: In our study, we included 100 children with vitamin D deficiency symptoms who attended the paediatrics department of our study institutions. Participants were categorized into four age groups: 1-3 years (30%), 4-6 years (15%), 7-10 years (21%), and 11-16 years (34%). The sample comprised 59% females and 41% males, with an average age of 12.84 years. Most were from middle-class families (39%), and 48% were in primary school. Common health issues included leg pain (58%), growth retardation (47%) and muscle pain/bone pain (39%). Vitamin D deficiency was prevalent, with rates of 50.00% in 1-3 years, 53.33% in 4-6 years, 47.62% in 7-10 years, and 61.76% in 11-16 years, indicating increased insufficiency with age. Conclusion: This study shows that vitamin D deficiency is high among our study children. A comprehensive action plan, including supplementation and food fortification, is crucial to prevent this deficiency in Bangladesh.