Background: The North American Research Committee on Multiple Sclerosis (NARCOMS) registry is a voluntary, self-report registry for people with multiple sclerosis (PwMS). There is growing interest in cannabis use by PwMS for management of various MS symptoms, particularly as cannabis products become more accessible. Objectives: To evaluate the prevalence of cannabis use for MS symptom management and factors associated with its use among current users in the NARCOMS registry. Methods: Active, US NARCOMS participants were invited to complete an online, supplemental survey regarding use of tetrahydrocannabinol-containing cannabis for their MS symptoms. This analysis explored the incidence of, and reasons for, using or not using cannabis, as well as behaviors and attitudes of current users. Findings were summarized using descriptive statistics. Results: Of 6934 participants invited, 3240 (47%) responded about their use of cannabis to treat symptoms of MS; 31% reported using cannabis for MS symptoms. Among the 69% of respondents who did not use cannabis for MS symptoms, the most common reasons were insufficient efficacy data (40%) or safety data (27%), legality concerns (25%), lack of insurance coverage (22%), or prohibitive cost (18%). Overall, 20% of respondents reported current use (within the last 30 days), on average 20 days in the past month. Of the primary administration modes for current users, the two most common were smoking (32%) or eating (20%). The most common target symptoms for use were spasticity (80%), pain (69%), and sleep (61%), with >95% finding cannabis very or somewhat helpful. Of current users, 51% reported using less cannabis than they otherwise might, with the most common reasons being prohibitive cost (54%) or lack of insurance coverage (47%). Conclusions: Although issues such as efficacy, safety, legality, and access constrain some PwMS from cannabis use for symptom relief, 31% have ever tried and 20% are currently using non-FDA-regulated cannabis products for MS. Of those currently using cannabis, most indicate it is helpful for treating spasticity, pain, and/or sleep. Funding: Greenwich Biosciences, Inc.