The aim of this study was to determine vertical transmission of Sterptococcus mutans (S. mutans) genotypes in mother-child pair. The present study was conducted on 60 mother-child pair saliva samples having at least three carious teeth. All enrolled preschool children were divided into two age groups Group-1 (1-3 years) and Group-2 (4-5 years). Stimulated saliva samples were collected from all enrolled subjects. After isolation of S. mutans DNA, Arbitrarily Primed Polymerase Chain Reaction (AP-PCR) and genotyping methods (with primers for the glucosyltransferase gene) were used to identify the matching and non-matching patterns of S. mutans genotypes transmitted from mother′s to their child. Statistical analysis showed 75% matching genotypes were found in Group-1 mother-child pair and 65 % was reported in Group-2 mother-child pair suggesting the presence of vertically transmitted strains of S. mutans higher in Group-1.