Bad oral habit is a habit that persists and is done repeatedly in the oral cavity. This habit is still common in elementary school age children. Most parents do not know that their child’s daily behavior is a bad oral habit. Dissemination is an effort to increase the knowledge and change the behavior. Parents with knowledge of bad oral habit enable to prevent the habit of persisting in their children so that children are prevented from the adverse impacts that can be caused by bad oral habit. The aim of this study was to know the difference of parental knowledge level on bad oral habit of children between before and after dissemination by lecture method using PowerPoint. This was a quasi-experimental study with pretest and posttest group design. This research was conducted at SD Karangjati in September-October 2017. The subjects of this research were mothers of students age 7-9 years who were studying in SD Karangjati. The subjects of the study were given a pretest questionnaire, then the dissemination was delivered and a posttest questionnaire was done after the dissemination. Based on the result of data analysis using Wilcoxon test, the p-value was 0.000 (p < 0.05) which means that there was a difference of parental knowledge level between before and after dissemination, where dissemination by lecture method using PowerPoint can improve parental knowledge about bad oral habit of children.