Recent studies reveal that secondhand cannabis smoke (SHCS) contains extremely high concentrations of air pollutants, such as particulate matter (PM), which are known neurotoxicants. This chapter reviews the current literature on the prevalence of SHCS exposure among youth, the concentrations of PM in SHCS, and the associated physical and neurobehavioral health outcomes. Prevalence rates of SHCS among children range from 1.6 to 42% across different samples. Extremely high concentrations of PM2.5 (>200 μg/m3) have been found for various cannabis methods of administration, including vaping, which is often considered safer than smoking. Children exposed to SHCS show higher rates of respiratory symptoms and infections, cognitive deficits, and behavioral problems compared to their unexposed peers. The literature review identified several gaps and future directions, including the need for mechanistic studies linking exposure to neurobiological outcomes, longitudinal studies assessing the impact of exposure across adolescence, and increased efforts to raise public awareness and education in community and healthcare settings. Addressing these gaps is essential for developing effective strategies to mitigate the adverse effects of SHCS on brain development and behavior in youth.