The goal of this study was to determine if there was a relationship between horse temperament and incidence of misbehavior due to the stress of being ridden by riders with a wide range of ability during the course of a camp season (9 weeks). It was hypothesized that horses with a social or aloof temperament would be able to adjust more easily while those with a fearful or challenging temperament would have higher incidence of misbehavior. At the beginning of the summer season at Timber Ridge Camp, Spencer, Indiana, the temperament of each horse (n = 15) was determined using on a rubric based on criteria developed by Barteau (2007). During the camp season, each rider was evaluated for riding skill level, and each incidence of equine misbehavior on trail rides was recorded as were the lengths of the trail rides. The scale for misbehavior was 0–4 with 0 = was not ridden, 1 = no incidents, 2 = annoyance (i.e., head tossing, ear-pinning, moving out of line), 3 = disruptive (i.e., balking, kicking, moderate shying), 4 = hazardous (i.e., bucking, bolting, rearing). The rider skill level was evaluated using a rubric based on Blokhuis et al. (2008) with a scale of 1–4, 1 = an advanced rider and 4 = total novice. The skill level of the rider was multiplied by the length of the rides in minutes to develop a stress index. One-way ANOVA showed a highly significant relationship (P < 0.0001) between the stress index and incidence of misbehavior. The behavior scale data for misbehaviors were combined due to lower frequency of severe misbehaviors 3–4. Horses with a challenging temperament exhibited significantly more misbehavior (P = 0.007) as did horses with a fearful temperament (P < 0.0001). Horses with social or aloof temperaments did not show any significant increase in misbehavior. The results support that in a summer camp horse program a positive relationship exists between stress and misbehavior of horses which varies with their temperament (P = 0.02). Horses with fearful or challenging temperaments appeared to be more stressed than horses with a social or aloof temperament based on their greater incidence of misbehavior. It is therefore recommended that horses be temperament tested before entering a summer camp program.