Probably yes... Greeks use the European Style two pin sockets and electricity comes at 220V, 50 Hz AC. So, if in your country you use different plugs then you 'll definetely need to get some power adapter with you. Most hotels in Athens will provide you with an adapter if you ask for it, but usually one is not enough. Of course you can still buy one at the electricity shops of the touristic areas or at the airport. Also, if you live in a country with 110 V do not forget that you will also need a power transformer to 220V.
