Introduction: By reduction or absence of the medial longitudinal arch in flatfoot deformity, a large part of the contact forces of the body weight transmit to the upper joints. The present study investigated weight distribution on the feet and the external moment around the ankle in women with flatfoot.Materials and Methods: The statistical population included women students aged 19 to 25 years in Alzahra University, Tehran, Iran. The control group was composed of twelve healthy women, and 37 with flatfoot deformity were divided into three experimental groups. Those in the experimental group 1 had unilateral flatfoot deformity, group 2 had rigid bilateral flatfoot deformity, and group 3 had flexible bilateral flatfoot deformity. The displacement of the center of pressure in the mediolateral and anteroposterior directions was calculated for assessing weight distribution on the feet and the external moment around the ankles. Force plate and 8 motion analysis cameras were used to collect data. MATLAB and SPSS software were used to calculate the displacement of the center of pressure and statistical analysis, respectively.Results: Experimental groups 2 and 3 and the control group significantly used the right foot for carrying body weight (P < 0.01); while in the experimental group 1, there was no significant difference in weight distribution on a flat or normal foot. There was no significant difference in the mean displacement of the center of pressure between the experimental and control groups. Only in experimental groups 2 and 3, there was a significant difference between the mean displacement of the center of foot pressure under the right and left feet (P = 0.02).Conclusion: Women with bilateral flatfoot are more subjected to external moment acting on one foot, which is the same foot that bears body weight in a standing position for a longer time.