This study investigates the effects of supplemental UV-B radiation on two high-cannabinoid Cannabis sativa L. cultivars—CBD-dominant ‘TJs CBD’ and CBG-dominant ‘Janets G’. The experiments examined varying doses and durations of UV-B exposure to assess their impact on plant growth, yield, and cannabinoid concentrations. Despite prior research suggesting potential benefits of UV-B in enhancing secondary metabolite production, the results revealed no significant effects on total cannabinoid content, plant growth metrics, or yield in either cultivar. The study indicates that the chemical profile of the cannabis plant does not substantially influence cannabinoid responses to UV radiation. These findings suggest that UV-B radiation, at the tested levels, does not enhance cannabinoid production in high-CBD and CBG cultivars. Future research could explore different light spectra or cultural management strategies to optimize cannabinoid production and consider UV-B's role in integrated pest management without adverse effects on plant health.