Background: Smoking is one of the reasons for melanin pigmentation in the oral mucosa. This study was done to determine the prevalence of oral melanin pigmentation in children and its association with passive smoking. Aim: To determine the prevalence of oral melanin pigmentation in children among 4–14 years of age and its association with passive smoking. Materials and methods: This observational study was carried out among 600 children from oral health screening camps conducted in the government schools of Waghodia district, Vadodara, Gujarat. Gingival pigmentation was assessed on the basis of the Dummett oral pigmentation index (DOPI), and evaluation of exposure to environmental tobacco smoke (ETS) was done by taking through history. Results: Gingival pigmentation was seen in 395 children (65.83%). The Chi-square analysis is used to find the significance of study parameters on the categorical scale. The analysis of variance (ANOVA) is used to find the significance of study parameters between the groups (intergroup analysis). About 23.50% showed no pigmentation, 24.80% showed mild clinical pigmentation, 23.50% showed moderate clinical pigmentation, and 26.30% showed heavy clinical pigmentation. Conclusion: According to the result of this study, we could conclude that there is correlation between passive smoking and oral-melanin pigmentation in children.