Aim: The aim of this study was to compare the level of mercury in the saliva of children with attention deficit/hyperactivity disorder (ADHD) as compared to age-and gender-matched controls in specific age groups. Materials and methods: A case-control observational study design was used. In school children with ADHD and outpatient dental clinics of a university dental hospital, the participants were schoolchildren diagnosed with ADHD studying in the first grade (6-7 years), sixth grade (12-13 years), and ninth grade (15-16 years) and were gender-matched to children without ADHD attending regular classes in school. Ninety children with ADHD comprised the test group while 90 children without ADHD comprised the control group. Results: In this study, we found that children with ADHD had higher levels of salivary mercury than their age-and gender-matched counterparts; however, this difference was significant only in the 6-7 years of age group. The regression model showed a mild positive association between salivary mercury and ADHD; however, the association was not statistically significant. Conclusion: While there is some indication that salivary mercury may be higher in children with ADHD, there is insufficient evidence to establish a definite association between the two. Clinical significance: The study highlights the need to evaluate existing evidence on the role of mercury, especially salivary mercury, in ADHD.