ObjectivesThe first permanent molar (FPM) is considered the tooth most susceptible to caries, as it is the first permanent tooth to erupt in the oral cavity, making it susceptible to environmental conditions that may appear as caries, hypoplasia, or hypomineralization. Several treatment options are available for managing deep caries, including root canal treatment (RCT). However, there is a lack of data on the success and failure rates of RCT in FPM among children. This study aimed to determine the success and failure rates of RCT in FPM among children and related factors. MethodsThis retrospective cohort study was conducted at three major centers in Jeddah, Saudi Arabia. Children aged 9–18 years who underwent an RCT between 2010 and 2019 were included. Clinical and radiographic examinations were also performed. ResultsBased on the loose criteria, most of the evaluated teeth (79.6%) were successfully treated. The treatment failed in only 20.4% of participants. Older patients and teeth with acceptable restoration quality had an increased success rate compared to younger patients and teeth with unacceptable restoration quality. A shorter time lapse between treatment and assessment resulted in a lower success rate compared to a longer time lapse. Based on strict criteria, 72.9% of the patients were successfully treated. The use of a microscope and teeth with acceptable restoration quality resulted in an increased success rate compared to teeth treated without the microscope and with unacceptable restoration quality. ConclusionsThe success rate of this procedure was high. Several factors, including older age, acceptable restoration quality, and the use of a microscope, increase the probability of success.