Objectives: To know the level of cotinine concentration in the saliva of children exposed to secondhand smoke and know the link between smoke exposure and gingivitis. Materials and Methods: The study was conducted on 100 children from Riyadh Colleges of Dentistry and Pharmacy between the ages of 6 - 12 years. A questionnaire was conducted on the parents of the children to find out their smoking behavior. The sample (children) was separated into two categories: category (A) children exposed to secondhand smoke as a test sample and numbered 50 children (23 boys and 27 girls), category (B) children not exposed to smoking as an ideal sample and numbering 50 children (24 boys and 26 girls). Index of dental plaque (calculus), gum index, presence of pigmentation and saliva sample collection were recorded from each child from the two groups. Furthermore, the level of cotinine in saliva samples was determined using the ELISA technique. Results: The concentration of cotinine in saliva is prominently present in samples of children category (A) compared to category (B). A positive correlation was observed between the number of cigarettes consumed and the concentration of cotinine in saliva. On the other hand, no relationship was found between gingivitis and the concentration ratio Cotinine. The likelihood of pigmentation in children exposed to secondhand smoking is 1.14 times higher than in other children. Conclusions: Secondhand smoke can raise the concentration of cotinine in saliva and stimulate the presence of pigmentation in children's gums.