Psychosocial factors influence family care and can jeopardize child development. This study aimed to analyze the association between maternal common mental disorders and incidence of early dental caries in preschool-age children living in areas covered by the Family Health Strategy in Salvador, Bahia State, Brazil, in a cohort design. A total of 472 children were examined and their mothers were interviewed from 2007 to 2008. Incidence of at least one tooth with caries was 21.19%, while 7.84% of the children showed high risk of caries. The results after adjusting for the child's age and maternal schooling showed that maternal common mental disorders were associated with high caries risk in deciduous teeth (adjusted RR = 2.41, 95%CI: 1.05-5.56, among children with 6 or fewer home appliances in the household; adjusted RR = 3.44, 95%CI: 1.06-11.17, among those that brushed twice or less per day). Maternal mental problems were associated with the development of caries in preschoolers.