Aim: To examine the relationship between salivary cotinine level and its effect on dental caries, oral hygiene, and dental behavior changes in children. Materials and methods: The study was conducted on 40 child patients and their parents from the outpatient department using a preliminary questionnaire comprising the demographic details and particular substance use details. With self-reported information from parents about the smoking habit, their children 7–12 years old were identified as passive smokers. Around 1–1.5 mL of unstimulated whole saliva was collected. Estimation of salivary cotinine was done using liquid chromatography and mass spectrometry (LC–MS). The selected subjects were also assessed for caries activity using the deft/dmft/DMFT index, Oral Hygiene Index-Simplified (OHI-S), and behavior assessment using Frankl's behavior rating scale. All the data were recorded and statistically analyzed. Results: Salivary cotinine was present in 35% (n = 14) and absent in 65% (n = 26). On comparing the salivary cotinine level with the status of dmft/ deft/ DMFT index the p-value was 0.003, whereas the p-value was insignificant for oral hygiene and dental behavior status in association with the salivary cotinine level. Conclusion: The salivary cotinine level was statistically significant with the prevalence of dental caries. However, the salivary cotinine level with oral hygiene was not statistically significant. No significant association was observed with the presence of salivary cotinine on the status of dental behavior of the children. Clinical significance: Attention needs to be paid to the ill effects of passive smoking (PS). Pediatric dentists need to know the parental tobacco use to assess a child's risk of oral health and behavioral changes as well.