The aim of this study was to investigate the effect of changes in pedal width (Q Factor) on knee frontal plane kinematics in cyclists with different Q angles. Three groups of 8 road cyclists (1- Low Q angle, 2- Normal Q angle and 3- High Q angle) cycled in four different pedal widths of 16, 19, 22 and 25 cm. The variables of maximum abduction, maximum adduction, range of motion and mean abduction/adduction angle of the knee joint during cycling were calculated. The results showed that there was significant difference between group 1 and group 3 in the variables of maximum, minimum and mean abduction angle of the knee joint. Also, the effect of changing in the Q Factor was significant on the variables of maximum, minimum and mean abduction of the knee joint. in all variables, the interaction effect between inter-group and between-group factor was not significant. The results of the present study showed that the difference in the Q angle of individuals and also the increase in pedal width affect the frontal plane knee joint kinematics; Therefore, in choosing the appropriate pedal width for cyclists, the difference in their Q angle should be considered.