The Internet has experienced a rapid increase in use globally. Specifically, more than 90% of Hong Kong's citizens use the Internet, and 70% of children in the age group of 6-17 years have daily access to it. However, internet addiction could pose serious social and health issues. Therefore, conducting research to investigate its causes and risk factors is fundamental. The current study examined the relationship between worry and Internet addiction among children in Hong Kong and investigated the moderating effect of the permissive parenting style on such a relationship. The participants consisted of 227 fourth- and fifth-grade students (120 males, 52.9%) with a mean age of 9.55 (standard deviation (SD) = 0.58) in Hong Kong. Each participant was asked to complete the questionnaires, including the Internet Addiction Test for Internet addiction, the Penn State Worry Questionnaire for Children for worry, and the Parental Authority Questionnaire for the permissive parenting style. The results indicated that worry was related to greater Internet addiction among children. Furthermore, there was a moderating effect of the permissive parenting style such that the positive association between worry and Internet addiction was stronger when the permissive parenting style was higher. Our findings imply that parenting styles are influential in the prevention of Internet addiction.