Background and ObjectivesGiven increases in youth cannabis and alcohol use and changes in the cannabis market, we examined parental openness and communication about cannabis and alcohol.MethodsAmong 197 participants who had children ≤18 years old and lived in six US metropolitan areas (Atlanta, Boston, Minneapolis, Oklahoma City, San Diego, Seattle), we examined sociodemographic and use correlates of parental openness (i.e., acceptability of child use, rules regarding use in the home or around children, communication) about cannabis and alcohol, as well as being more open about cannabis versus alcohol.ResultsIn this sample (Mage = 32.30, 70.1% female, 30.5% sexual minority, 33.0% racial/ethnic minority, 41.6% in recreational cannabis state), 33.5% reported past‐month cannabis use, and 59.9% alcohol (22.8% used both, 29.4% used neither). Multivariable regression indicated that cannabis users (vs. nonusers) and sexual minority (vs. heterosexual) individuals were more open about cannabis use; alcohol users (vs. nonusers) were more open about alcohol use. Additionally, older parental and child age correlated with greater cannabis‐ and alcohol‐related communication, and females (vs. males) reported greater cannabis‐related communication. Those married/cohabitating and reporting past‐month alcohol use were less likely to allow cannabis versus alcohol in the home or near children. Parents in legalized recreational (vs. nonlegalized) states, females, and heterosexual individuals reported greater cannabis‐ versus alcohol‐related communication.Discussion and ConclusionsInterventions are needed to support parental communication regarding substance use, particularly cannabis.Scientific SignificanceThis study addressed parenting and youth substance use during evolving cannabis legislation and can inform youth substance use prevention interventions targeting parent‐child communication.