Objective. The purpose of this study was to examine the effect of Kinesiophobia level on postural stability during Single Leg Squat Test (SLST) in females with patellofemoral pain syndrome (PFPS). Methods. Forty women with PFPS were divided into a High Kinesiophobia level group (HK), a Low Kinesiophobia level group (LK), and a pain-free control group of twenty participants. Postural stability was measured during the performance of the Single Leg Squat Test (SLST) on a force platform. The centre of pressure (COP) excursion and velocity were recorded. Results. The HK group had a significantly higher mean medial–lateral and anterior-posterior COP displacement compared to the LK and control groups. However, the results showed no significant differences in COP variables (velocity and displacement) between LK and healthy subjects. Muscle strength of participants with PFPS presented a significant deficit compared to healthy control group. Conclusions. High Kinesiophobia negatively affects postural stability during the SLST. Kinesiophobia should be considered during the assessment and management of PFPS.