The aim of this study was to compare emotional excitability in purebred Arabian racehorses trained either with a standard method or with additional off-racetrack training. The study was carried out on 46 horses that were trained for racing in a home stud. The control group (CN, n = 23) was trained only on the training racetrack, whereas for the experimental group (EX, n = 23), the training schedule was alternated between work on the training track and off-racetrack training in a forest. The emotional excitability in horses was determined according to the heart rate (HR) and heart rate variability (HRV). The measurements (six times every 30 d) were taken at rest, during grooming and saddling, and during mounting and walking with a rider. The behavior of horses was also assessed. Higher activity of the parasympathetic nervous systems was found in EX horses during procedures preceding the training. This effect disappeared and the results paralleled those of CN horses once the training session with a rider began. The tested modification of the race training had a positive impact on the horse behavior of the horse during grooming, saddling, mounting, and walking with a rider. However, the modification influenced the autonomic system activity of horses only at rest and during the procedures preceding training sessions, whereas the effect was not seen during mounting and walking.