A search operation is under way in the Puffin Island area.
A Coastguard helicopter from Caernarfon as well as rescue teams from Penmon and Bangor have been sent following a report that the aircraft had gone missing at around 12.47pm.
RNLI lifeboats from Beaumaris, Moelfre and Llandudno, as well as officers from North Wales Police, are also involved in the search.
It has not been confirmed how many people were on board the aircraft.
North Wales Police said it received a call at 12.59pm reporting a possible crash involving a light aircraft in the Penmon area.
A statement added: "Officers are currently assisting HM Coastguard and our enquiries are ongoing."