Even though avocados are healthy for humans, discover whether they're safe for dogs & cats (including details on potentially harmful ingredients for pets).
www.hillspet.com
Personally I would never even consider giving my cat avocado...in ANY quantity...but that is just me.
So, read the article , google some more and you will find your answer ,I am sure.
I actually have just been reading various sites, and it seems that if he only gets the 'soft' part and no skin or pits, etc, he should be fine... or did I miss something?