Explorations into horse personality have only recently occurred with questionnaire inventories demonstrating to be the most effective way of rating personality in animals. Recent equine studies are based on the findings from human studies, and look at the relationships between personality and performance in different disciplines,such as sports. These studies have shown that horse-rider personality compatibility is essential for maximising performances in sport. The current study focuses on this personality compatibility in relation to polo, with 104 polo players completing personality questionnaires. The horses used were a mixture of low, medium and high goal ponies from across the country with a total of 129 horses being rated using the Horse Personality Questionnaire. The raters were the full time carers of the horses. A univariate general linear model was used to test for main effects and interactions of human and horse personality on the player’s handicap and the level of polo played by the horse. The results show that horse intellect produced a negative main effect on the player’s handicap and also on the level of polo that the horse plays. Both player neuroticism and player openness produced negative main effects on the player’s handicap and also on the level of polo played by the horse. There was a positive interaction between player neuroticism and horse neuroticism, and between player openness and horse intellect in determining the outcome of the player’s handicap. Additionally, there was a positive interaction between horse intellect and player openness in determining the level of polo played by the horse. These rider-horse interaction studies provide unique opportunities to examine the affects of compatibility between humans and animals. This demonstrates that a horse will match better with one rider than with another and hence is more likely to be selected and trained for their right discipline.