Background: The flattening of the foot's medial arch is known as acquired flatfoot. It's one of the most common problems seen among adult health-care providers. Objective: The purpose of this study is to determine the tibialis posterior muscle endurance among physiotherapist with flatfoot. Methodology: The observational study included 60 physiotherapists who met the inclusion criteria. The single legged heel rise test and the foot posture index were used to evaluate each individual with flatfoot.