Muscle strength may play an important role in endurance road cycling events. By increasing lower body strength and power, the anaerobic energy production and maximal levels of muscular force required during races to climb hills, perform repeated surges in pace, or in the final sprint may improve. While strength training is often performed by highly trained cyclists, the scientific literature supporting this practice is subject to a number of methodological limitations and potentially confounding variables that raise doubts over the efficacy of strength training to enhance performance in this population. The purpose of this review is therefore to identify and evaluate original research examining the influence of strength training on road cycling endurance performance in highly trained cyclists. Using relevant databases and keywords, nine training studies met the inclusion criteria and were reviewed. Grade B-level evidence indicated that following performance of strength training, highly trained road cyclists can significantly improve performance variables such as lactate power profile, oxygen cost or consumption, cycling economy, work or exercise efficiency, as well as peak and mean power outputs during time trials lasting between 30-seconds and 4-kilometres. Grade C evidence also suggests mean and average power outputs during time trials ranging from 40 to 60 minutes, and time to exhaustion at maximal aerobic power or 80-85% VO2max are improved. However, the physiological mechanisms responsible for these improvements are unclear. Future research is also necessary to determine what is the best form(s) of strength training for these athletes, and how best to incorporate such training into their annual periodized training plan.