Cannabis continues to be the second most popular substance used among adolescents and young adults. This onset of use occurs during a sensitive period of adolescent neuromaturation, which is partially driven by the endogenous endocannabinoid system. Preclinical evidence has suggested increased vulnerability for cannabis-induced neurocognitive effects during this sensitive developmental stage. Cumulative cross-sectional and longitudinal research has linked regular cannabis exposure during adolescence and young adulthood with subtle declines in IQ, verbal memory, attention, processing speed, and facets of executive functioning. These cognitive decrements are more pronounced in heavier users and associated with an earlier age of cannabis initiation. In addition, prospective twin studies have questioned whether cannabis directly causes these cognitive decrements or if they are attributable to shared familial risk factors linked with cannabis use onset. Finally, the impact of cannabis appears to be complex and related to multiple factors, including the total exposure, delta-9-THC potency, cannabinoid content, age of onset, extent of substance co-use, sex of the user, and existence of medical or psychiatric comorbidities. Larger-scale, prospective longitudinal studies are needed to fully characterize the impact of various cannabis use patterns on cognition during this critical period of development.