Purpose: Maintaining balance in humans involves continuous changes in parameters. The aim of this study was to assess the effect of hippotherapeutic exercises on development of the sense of balance in boys aged 15 to 17 years with mild intellectual disability. Methods: The study examined 50 randomly chosen boys aged 15 to 17 years with mild intellectual disability from the special education centre in Leżajsk, Poland. The study participants were divided into two groups: experimental group, who participated for 3 months in hippotherapeutic classes and the control group, with boys attending outdoor or indoor physical education classes. Before and after completion of the study, both experimental and control groups were diagnosed by means of Accu SwayPlus force plate. The force plate was used to determine alterations in the position of the centre of pressure (COP) on the platform in the frontal and sagittal planes in relaxed standing position with feet spread to the shoulder width and with eye control with respect to the base of support (BOS). The description was based on mean displacement of the centre of gravity (COG), mean velocity of displacements of the COG, mean radial displacement and total length of the COP pathway. Results: In the experimental group, equestrian exercises induced a series of significant changes that pointed to the improved balance reactions. The character of these changes in the positions analysed was similar: values of body sway in the sagittal plane and their range and mean displacements decreased statistically significantly after training. The same tendency was observed for mean radial displacements in the free open position and with closed support surface. Furthermore, the velocity of displacement and the length of the COP’s projection pathway on the support surface in the free open position was also reduced. All significant changes and trends found for the experimental group, which occurred after 3 month of hippotherapeutic classes, suggest improved parameters of balance. Conclusions: The lack of changes in balance parameters in the control group shows that the hippotherapeutic classes significantly develop balance abilities in boys aged 15 to 17 years with mild intellectual disability.