Oral health is a prerequisite for the rehabilitation of children with oral cleft (OC). Thus, caries negatively affects individuals with OC. This study aimed to investigate dental caries in children with OC, determining the first period of the most significant susceptibility to caries. This cross-sectional study evaluated caries' prevalence and mean dmft in the primary dentition of 300 children with OC, distributed among ten groups at six-month intervals. The exams were carried out using the WHO diagnostic criteria. Fisher's exact test and Student's -test were used for statistical comparisons with a significant level of 5%. The caries prevalence in the total group was 59.4%, and the dmft was 3.4. The first period of susceptibility occurred between 13 and 18 months and 19 and 24 months, with a prevalence ranging from 6.6% to 40% ( < 0.05) and a dmft ranging from 0.1 to 1.0 ( < 0.05). The prevalence and dmft increase with age. Our findings suggest that in children with OC, the first period of susceptibility to caries occurs from 13 to 18 months. These findings demonstrate the need for pediatric dentistry to establish an early preventive protocol for children with clefts during the first year.