Upper extremity dysfunction is frequently seen in Parkinson's disease (PD). Existing research has shown that bradykinesia, which is main symptom of PD, is primarily responsible but the combined effects of spinal posture and axial rigidity on upper extremity functions were not investigated yet. The aim of this study was to investigate upper extremity functions in patients with PD and to evaluate relationship of these with spinal posture and axial rigidity. This prospective controlled study included 40 patients with PD and 40 healthy controls. Upper extremity function was measured with the 9-Hole Peg Test. Spinal posture and axial rigidity were measured with a Spinal Mouse. Compared with the control group, a decrease in upper extremity functions (p < 0.001), decreased lumbar lordosis (p = 0.003), and posterior sacral tilt (p = 0.021) were determined in patients' group. Thoracic and lumbar mobility in the sagittal (all p < 0.001) and frontal planes (p = 0.004, p < 0.001) was found to be reduced in the patient group. A correlation was determined between upper extremity functions and lumbar mobility in the sagittal (p = 0.022, r= -0.362) and frontal planes (p = 0.045, r= -0.319) and lumbar lordosis (p = 0.048, r = 0.302). The results of this study demonstrated that altered spinal posture and increased axial rigidity were related with decreased upper extremity functions in patients with PD. There is a need for further studies to investigate effect of trunk-based therapies on upper extremity function in patients with PD.