Background: Upper limb impairment affects activity and participation in children with unilateral cerebral palsy (UCP). Pressure garment therapy (PGT) using compressive dynamic Lycra (R) garments is an innovative intervention proposed for the management of cerebral palsy consequences. The PROPENSIX study aims to evaluate the efficacy of a therapy using a Lycra (R) sleeve as compared to a placebo sleeve to improve bi-manual performance measured by the Assisting Hand Assessment (AHA) in children with unilateral cerebral palsy. Methods: The PROPENSIX trial is a multicenter, prospective, placebo-controlled, double-blinded, randomized study. One hundred children with UCP, aged from 5 to 10, are randomly assigned as soon as they are recruited in a 1:1 ratio to perform usual daily activities, especially activities involving bimanual performances, with Lycra (R) sleeve or placebo sleeve during 6 months. The primary endpoint is the change in bimanual performance from inclusion to 6 months, evaluated by AHA. The secondary endpoints evaluate changes from inclusion to 6 months in other dimensions of the International Classification of Functioning (ICE), upper limb movement capacity assessed by Quality of Upper Extremity Skill Test (QUEST), and health-related quality of life evaluated by Pediatric Quality of Life Inventory 3.0 Cerebral Palsy Module (PedsQLTM 3.0 CP Module) and in body structures and functions domain assessed by neuro-orthopedic examination and somatosensory evoked potentials (SEP). Discussion: The PROPENSIX study is the largest randomized controlled trial (RCT) aiming to evaluate the efficacy of a PGT using compressive dynamic Lycra (R) sleeve in UCP. Enhancement of children's bimanual performance at the end of the 6 months wear of the Lycra (R) sleeve should improve evidence regarding this type of treatment and expand discussion about their recommendation in clinical practice. Data from secondary outcomes assessments should bring interesting arguments to discuss the Lycra (R) sleeve action on mobility, tonus, and sensory impairments in children with unilateral cerebral palsy.