Objective: The general treatment approach for Parkinson's disease (PD) is L-dopa administration. While L-dopa only relieves dopaminergic deficiency, it has no effect on the serotonergic system, which is thought to be impaired in the disease. The limitations of current treatment methods have made it necessary to discover new approaches to the treatment of the disease. Studies conducted in recent years report that different types of exercises applied lead to improvement in the symptoms of PD. Exercising decreases serotonin levels and increases dopamine levels. However, the effect of exercise on serotonin levels together with dopamine in PD and its effect on non-motor symptoms such as anxiety and depression are unknown. Methods: PD is created using MPTP. The exercise groups were given challenging treadmill exercises for 6 weeks. Serotonin and dopamine levels were measured in the striatum and serum. Parkinson's symptoms were examined with pole test and behavioral tests. Results: Exercise significantly reduced bradykinesia, increased motor activity, and decreased anxiety behaviors in the exercise groups. While exercise increased striatal dopamine levels in all exercise groups, there was no difference in striatal serotonin levels. However, the serotonin serum level was decreased in the PD model group. While treadmill exercise increased striatal dopamine levels in the Parkinson's mouse model, it did not cause any change in striatal serotonin levels. However, the decrease in serum serotonin level was determined only in the MPTP group. Conclusion: The fact that the decrease in serotonin level was only in the disease group and the lower level of anxiety observed in behavioral experiments suggested that regular treadmill exercise was the reason. However, this improvement was not observed in cases where the anxiety level was very high.