Exposure to cigarette smoke in the home environment remains a significant health problem and is a major risk factor for acute respiratory infections (ARI), pneumonia, and growth disorders in toddlers. As passive smokers, toddlers are particularly vulnerable to the negative effects of cigarette smoke because their respiratory and immune systems are not yet fully developed. Mothers play a central role in protecting infants from exposure to cigarette smoke, so the level of mothers' knowledge is an important predisposing factor in the formation of preventive behavior. This study aims to determine the level of mothers' knowledge about the dangers of cigarette smoke exposure to toddler health. This study uses a quantitative descriptive design with a cross-sectional approach. The study population consisted of all mothers with toddlers in Abuan Village, Bangli Regency, totaling 288 people, with a sample of 168 respondents selected using purposive sampling. Data were collected using a closed questionnaire that had been tested for validity and reliability and analyzed univariately. The results showed that most mothers had a good level of knowledge about the dangers of exposure to cigarette smoke on the health of toddlers (98.8%). Most respondents had a high school education (67.9%) and worked as housewives (37.5%). The level of mothers' knowledge about the dangers of cigarette smoke exposure to toddler health was in the good category for 166 people (98.8%), while the rest were in the poor category.