Equestrian sports are unique because they are based on the interaction of the horse-rider dyad. Anecdotal evidence suggests that appropriate mental attributes of the rider contribute considerably towards achieving effective communication between horse and rider. This thesis aims to determine which and to what extent psychological traits and states of equestrian riders play a role in horse-rider performance. Part I of the thesis determines that equestrian riders exhibit a unique personality profile. Personality traits also seem to affect how riders perceive their horses' temperaments. Elite riders show superior abilities to cope with stressful situations, a trend which was examined more closely in part II: Differences in precompetitive levels of arousal and mood states between more advanced and novice riders were determined. Furthermore, intensity levels and directional interpretations of somatic and cognitive arousal were shown to have an effect on competitive performance. Riders' interpretation of their horses' temperament were also shown to be correlated to elements of arousal and competitive performance. Practical implications are that in order to improve horse-rider communication and to achieve optimal performance, less competent riders should develop relevant coping strategies to control levels of arousal. Part III explored the use of and differences in psychological skills at different competence levels in equestrian sports. Elite riders demonstrated more comprehensive coping strategies than non-elite riders. On that basis, a psychological skills training program was developed and administered to amateur riders. Improved competitive performance 'following completion of the program confirmed that psychological skills training can play an important role in equestrian sports. In conclusion, the current thesis provides some evidence regarding the role psychological states and traits play in equestrian sports. Equestrian riders of all disciplines may be well served to spend time honing their own psychological skills in order to optimize their relationship with their horses.