Kecleon can be found in Routes 118, 119, 120, 121 & 123, as well as by the Devon Scope on 120 (going down to the water and on the bridge - Steven will guide you to the latter). You startle one in Fortree (on the way to the gym), but it leaves.
you can find a kecleon in fortree city.
u cant!
You go past Fortree city and go through some more tall grass and there will be a bridge. Go down the bridge and Steven will give you the DEVON SCOPE.
mauvile city
It's an invisible Pokemon called Kecleon you can only reveal it with the Devon scope.
in the cave where aaron are found
Kecleon. If you have a Devon Scope, talk to the 'invisible thing' and you can use it.
You deliver Devon's Goods to Captain Stern who is in Slateport City's museum.
If given to the Devon researcher in the Devon corporation the claw fossil can be revived into Anorith.
head back to the Devon building to report mission sucsess
On the first floor on Devon building, there is a dude on the computer who revives them
Answer:Go to Route 120 and go south. Cross the bridge, and you'll see Steven. After a battle with his Kecleon, he'll give you the Devon Scope. It alows you to see any unseeable Pokemon. Now go back to the gym in Fortree City, and press "A" to the place where you can't get in. The Devon Scope is automatically used, and you'll see a Kecleon getting away.
The Devin Co. is in Rustboro City
You can find Devon in Mossdeep City he will give a Beldum. Note: Also works for Ruby and Sapphire.