Marijuana is currently legal for recreational use in 10 states and Washington DC while a total of 34 states have implemented varying degrees of medical marijuana. The commercialization of marijuana has been accompanied by a proliferation of false claims regarding the therapeutic potential of marijuana, which are popularized by several different information sources. To date, no study has examined where US adults get their information regarding marijuana. To determine the sources of information associated with believing unsupported claims about marijuana. Probability-based online survey PARTICIPANTS: 16,820 adults, with a response rate of about 55% (N = 9003) MAIN MEASURES: Most influential sources of information about marijuana and belief of statements consistent with misinformation, for example, smoking marijuana has preventative health benefits, secondhand marijuana smoke or use during pregnancy is completely or somewhat safe, and marijuana is not at all addictive. There were 9003 respondents (response rate 55%). Forty-three percent believed unsupported claims about marijuana. The most influential sources of information were health professionals, traditional media, friends/relatives, and social media/internet. Individuals reporting social media or the Internet (1.46 CI [1.30, 1.64]), the marijuana industry (e.g., advertisements, dispensaries) (2.88 CI [2.15, 3.88]), and friends or relatives (1.41 CI[1.26, 1.58]) as the most influential source of information about marijuana were more likely to believe any statement consistent with misinformation about marijuana in comparison with those who reported other sources as most influential. Individuals reporting the most significant source of information regarding marijuana was from social media or the Internet, the marijuana industry, or friends or relatives were more likely to believe unsupported claims about marijuana. Public health campaigns to counter the misinformation about marijuana to the public are needed.