Lifetime psychedelic substance use has previously been linked to nature relatedness and pro-environmental behaviour. Yet, participants’ responses to the self-report measures in these studies may have been affected by stereotypical associations or confirmation bias. We therefore re-examined this link by measuring three pro-environmental dependent variables: nature relatedness, concerns about climate change, and objective knowledge about climate change. Additionally assessing lifetime experience with 30 psychoactive substances, we collected an international convenience sample for an online survey (n = 641), Controlling for age, educational attainment, and covariation in substance use indicators, psychedelic use (primarily the use of psilocybin) predicted objective knowledge about climate change directly, and indirectly via nature relatedness. Further, it predicted concern about climate change indirectly via nature relatedness. The results suggest that the relationship of psychedelics with pro-environmental variables is not due to psychological biases, but manifests in variables as diverse as emotional affinity towards nature as well as knowledge about climate change.