The aim of this study was to test the clinical utility of the 6-min walk test (6MWT) for patients with moderate Parkinson’s disease (PD) through a determination of factors related to this test. This was a descriptive, observational study carried out at a General Hospital, in-patients. Twenty-four patients with moderate PD were studied. We used Hoehn and Yahr stage ratings (HY stage), Unified Parkinson Disease Rating Scales (UPDRS) motor examination score, 6MWT, Berg Balance scale, Timed ‘Up & Go’ test (TUG), 10-m walk test (10-m walk speed, 10-m walk steps and cadence), and the energy cost of walking (Ec). The average HY stage was 3.1±0.5 and 6MWT was 340.8±110.9 m. TUG (r=−0.68, P<0.01) and Ec (r=−0.65, P<0.01) were correlated significantly with 6MWT. Multiple regression analysis with age, HY stage, TUG, cadence, and Ec as variables indicated a significant degree of variability in the 6MWT results (R2=0.77, P<0.001). The TUG (β=−0.47, P<0.01) and Ec (β=−0.4, P<0.01) were correlated independently with the 6MWT results. In contrast, age, HY stage, and cadence were not independently correlated. The 6MWT is a simple tool for assessing walking capacity for patients with PD. In this study, we confirmed the convergent validity and clinical utility of the 6MWT for patients with moderate PD. The 6MWT is useful for clinical assessment to guide the planning of rehabilitation treatment for patients with moderate PD.