BACKGROUND: Pisa syndrome (PS) is a clinical condition frequently associated with Parkinson's disease (PD). It is characterized by a trunk lateral flexion higher than 10 degrees and reversible when lying. One pathophysiological hypothesis is the altered verticality perception, due to a somatosensory impairment. Osteopathic Manipulative Treatment (OMT) manages fascial-system alterations, linked to somatic dysfunctions. Fascial system showed to be implicated in proprioceptive sensibility. OBJECTIVE: The aim of the study was to assess OMT efficacy on postural control in PD-PS patients by stabilometry. METHODS: In this single-blinded trial we studied 24 PD-PS patients, 12 of whom were randomly assigned to receive a multidisciplinary physical therapy protocol (MIRT) and sham OMT, while the other 12 received four OMT plus MIRT, for one month. The primary endpoint was the eye closed sway area assessment after the intervention. Evaluation of trunk lateral flexion (TLF) with DIERS formetrics was also performed. RESULTS: At one month, the sway area of the OMT group significantly decreased compared to placebo (mean delta OMT - 326.00±491.24 mm2, p = 0.01). In the experimental group TLF showed a mean inclination reduction of 3.33 degrees after treatment (p = 0.044, mean d = 0.54). Moreover, a significant positive association between delta ECSA and delta TLF was observed (p = 0.04, r = 0.46). DISCUSSION: Among PD-PS patients, MIRT plus OMT showed preliminary evidence of postural control and TLF improvement, compared to the control group.