The aim of present study was to determine assertiveness and aggression level of soccer players in different age groups. Participants were 150 amateur soccer players between ages of 14 to 30 years. Assertiveness and aggression level of participants were measured by Aggression Inventory which was developed by Kiper (1984). Three dimensions and 30 items (10 items per subscale) comprised the inventory. Subscales of the inventory are called as destructive aggression, assertiveness and passive aggression. Inventory was administered players in three different categories of amateur soccer league in Antalya (Junior, Youth and Senior).