Objective: Identify the incidence and risk factors of vitamin D deficiency/vitamin D insufficiency in children aged 1–5 years. Methods: A cross-sectional survey was conducted among children between the ages of 1 and 5 in the Bope-Poddala and Galle municipality areas. The sample was obtained by cluster sampling method. Data on socio-demography, pregnancy, sun exposure, and diet were obtained. Serum 25(OH)D concentrations were measured and the cutoff value was determined as per the global consensus in 2016. Results: Among 100 children, the mean serum 25(OH)D level was 86.4 nmol/L (24.06 ng/mL). The prevalence of vitamin D deficiency and vitamin D insufficiency was 7% and 28%, respectively. Birth weight and sunlight exposure were significantly different among vitamin D deficiency/vitamin D insufficiency and sufficient groups. Both were found to be risk factors for vitamin D deficiency/vitamin D insufficiency in logistic regression. Conclusion: Vitamin D deficiency/vitamin D insufficiency is significant among children aged 1–5 years and decreased sun exposure and low birth weight are the main risk factors.