Background: The North American Research Committee on Multiple Sclerosis (NARCOMS) registry is a voluntary, self-report registry for people with MS (PwMS). There is growing interest in cannabis use by PwMS for management of various MS symptoms, particularly as cannabis products become more accessible. However, it is unclear how PwMS are obtaining medical guidance and product information. Objectives: To evaluate how PwMS obtain medical information on cannabis and how PwMS view the role of their healthcare provider as an information source. Methods: Active, US NARCOMS participants were invited to complete an anonymous online, supplemental survey regarding use of tetrahydrocannabinol (THC)-containing cannabis for their MS symptoms. This analysis explored the source of medical guidance for cannabis use and product information for current users, as well as their resulting product preferences. Findings were summarized using descriptive statistics. Results: Of 6934 participants invited, 3240 (47%) responded about their use of cannabis to treat symptoms of MS; 636 (20%) of respondents were current users (had used cannabis for MS symptoms within 30 days of survey administration). Most current users (75%) had discussed cannabis with their physician, but the most frequent primary source of medical guidance for cannabis use was nobody/self (47%). Other primary sources of medical guidance included a dispensary professional (20%), an MS physician (12%), or a physician other than the MS provider (11%). The most common information sources used to determine what exactly is in the cannabis/marijuana product were dispensaries (45%), dealer/friends (31%), and product labels (27%). Current users reported that they most often obtained their cannabis products from dispensaries (62%), followed by family/friend (18%) or acquaintance (13%); the most important factors in selecting a product were quality/safety (70%), access to preferred potencies/formulations (40%), and location close to home (39%). The most preferred types of cannabis were equal THC and cannabidiol (31%) and high THC/low cannabidiol (30%). Conclusions: People with MS who use cannabis commonly discuss its use for MS with their physicians, but medical guidance and information about cannabis product content is most often either not sought or sought from individuals other than their healthcare providers.