A potential challenge associated with sports is that athletes must often perform the cognitive processing associated with decision-making (i.e., movement selection) when fatigued. The purpose of this systematic review was to summarise studies that have analysed the extent to which fatigue influences the effects of decision-making on lower extremity mechanics during execution of common sports manoeuvres. We specifically focused on mechanics associated with ACL injury risk. Reviewers searched the PubMed, SPORTDiscus, CINAHL and Web of Science databases. The search identified 183 unique articles. Five of these articles met our eligibility criteria. Two of the studies incorporated fatigue protocols where athletes progressed to exhaustion and found that the effects of decision-making on mechanics were more pronounced with fatigue. The nature of the results appears to indicate that fatigue may compromise an athlete's cognitive processing in a manner that diminishes their ability to control movement when rapid decision-making is required. However, three subsequent studies utilised fatigue protocols designed to mimic sports participation and found that fatigue did not influence the effects of decision-making on mechanics. In general, these findings appear to indicate that fatigue may only affect the cognitive processing associated with decision-making when athletes approach a state of exhaustion.