The endocannabinoid system (ECS) is a widespread neuromodulatory system that plays a crucial role in maintaining homeostasis in the human body. It is a complex network of endocannabinoids (eCB-s), cannabinoid (CB) receptors and enzymes responsible for their biosynthesis and degradation. The dynamic course of brain maturation, particularly synaptic potentiation and pruning, occurs during the transition from adolescence into early adulthood. Evidence suggests that changes in eCB signalling contribute to these processes. Exogenous CB-s, such as tetrahydrocannabinol (THC), exert their biological effects through their interactions with CB receptors. Youth is also a period of higher vulnerability for exposure to THC. This review will provide an introduction to the ECS with an emphasis on its role in synaptic plasticity, neurotransmission, as well as on how THC exposure can potentially disrupt the function of the ECS, especially during adolescence.