Background & Aims: The purpose of this study was to determine the immediate effect of patella support brace on co-contraction and electromyographic activity of selected lower limb muscles in females with patellofemoral pain syndrome during stance phase of gait. Methods: EMG activity of vastus lateralis, vastus medialis, rectus femoris, gastrocnemius, biceps femoris, semitendinosus, gluteus medius and gluteus maximus of 16 females with patellofemoral pain syndrome (mean age: 23.94±1.93 years) before and after wearing the patella support brace were compared using paired t-test. Results: EMGrms activity of vastus medialis significantly increased after using patella support brace during stance phase of walking (p=0.049). Semitendinosus muscle showed significantly lower EMGrms activity in bracing condition during loading response phase (P=0.045) and total stance phase (P=0.03). During midstance and propulsion, none of the selected muscles showed significant difference between before and after wearing the knee brace conditions. The results showed no significant differences in co-contraction between vastus lateralis and vastus medialis (P=0.497) and between medial (vastus medialis, semitendinosus) and lateral muscles (vastus lateralis, biceps femoris, gastrocnemius) of the knee (P= 0.088) in with versus without brace use condition. Conclusion: Because of increase of vastus medialis activity and decrease of semitendinosus activity in bracing condition during stance phase, it is possible to peak knee extensor moment increase during stance phase of gait by using Patella support brace.