Background: Apathy occurs frequently in patients with Parkinson’s disease (PD), and has a negative impact on activities of daily living through loss of motivation. Pramipexole (PPX), which shows preferential affinity for D3 dopamine receptor in the mesolimbic system, is thought to influence mood and motivation. Therefore, we conducted an open-label case-control study to examine the effect of PPX on apathy in PD. Methods: We studied 36 PD patients (mean age, 70.4 ± 8.1 years), who had been treated only with L-DOPA. PPX was added to L-DOPA treatment in 24 patients (PPX group) and other 12 patients continued with L-DOPA alone (non-PPX group). The study period was 8 weeks. Apathy was assessed using the revised apathy scale for Japanese. Motor function was assessed with part III of the Unified Parkinson’s Disease Rating Scale (UPDRS). Results: Seventeen of 36 patients (47%) were diagnosed as having apathy. In the PPX group, apathy scale significantly improved from 17.3 to 13.8 at week 8 (p < 0.05). Motor function also improved significantly from 16.1 to 7.6 at week 8 (p < 0.0001). In the non-PPX group, apathy scale and UPDRS both showed no change during the study period. There was no correlation between changes in apathy scale and UPDRS in either the PPX or non-PPX group. Conclusion: PPX may be effective for treating apathy as well as motor dysfunction in PD.