Bladder dysfunction (urinary urgency/frequency) and bowel dysfunction (constipation) are common non-motor disorders in Parkinson's disease (PD). In contrast to motor disorder, the pelvic autonomic dysfunction is often non-responsive to levodopa treatment. Brain pathology mostly accounts for the bladder dysfunction (appearance of overactivity) via altered dopamine-basal ganglia circuit, which normally suppresses the micturition reflex. In contrast, peripheral enteric pathology mostly accounts for the bowel dysfunction (slow transit and decreased phasic contraction) via altered dopamine-enteric nervous system circuit, which normally promotes the peristaltic reflex. In addition, weak strain and paradoxical anal contraction might be the results of brain pathology. Pathophysiology of the pelvic organ dysfunction in PD differs from that in multiple system atrophy; therefore it might aid the differential diagnosis. Drugs to treat bladder dysfunction in PD include anticholinergic agents. Drugs to treat bowel dysfunction in PD include dietary fibers, peripheral dopaminergic antagonists, and selective serotonergic agonists. These treatments might be beneficial not only in maximizing patients' quality of life, but also in promoting intestinal absorption of levodopa and avoiding gastrointestinal emergency.