In Counter-Strike Global Offensive, (CS:GO or CS:Source), friendly fire is turned off by default. In this article we will show you how to turn on friendly fire in CS:GO if you want to turn it on, or switch between settings.
How to enable friendly fire?
To turn Friendly Fire option on/off:
Open the console and type:mp_friendlyfire <0/1>
With 0 being off, and 1 being on. This allows you to switch between both modes.
Can you enable friendly fire in casual mode?
Unfortunately, no, you cannot enable friendly fire in casual play. Friendly fire is only enabled in competitive gameplay. That said, if your intention is to team kill you risk getting kicked and banned from your own server.