Background: Dental fluorosis is considered mostly as an aesthetic issue that has an adverse impact on the children’s psychological health and self-esteem. The current study aimed to assess the prevalence of dental fluorosis and the association between using bottled water in infants’ formula and dental fluorosis risk factor in infancy among school children aged between 7 and 13 years in Riyadh city. Methodology: An epidemiological questionnaire-based study was carried out among students at primary public schools in Riyadh, Saudi Arabia, using a survey that was distributed to 389 primary public schools. Almost 201 students were examined using an oral diagnosis kit and an ordinary light provided by our college. The surveys were collected, and the data were analyzed using the Statistical Package for the Social Science program. Results: Out of the 201 school children who were aged 7-13 years, 124 (61.7%) had dental fluorosis, 77 (38.3%) were without fluorosis, and the fluorosis’ prevalence increased in the central incisors for 36 children (17.9%). The number of children (72) with fluorosis who used boiled bottled water with milk formula was higher than the number of children (42) with no fluorosis and who used boiled bottled water with milk formula.Conclusion: In the present study, children aged 7-13 years showed a higher prevalence of dental fluorosis (61.7%). The prevalence of dental fluorosis increased in the central incisors (36, 17.9 %), followed by the first permanent molars (31, 15.4 %), and in both (37, 18.4%). Mothers should use distilled/deionized water for reconstitution of infant formula to reduce fluoride intake.