Killer whales, Orcinus orca, are known to be one of the most widespread cetaceans, inhabiting all the oceans of the world, but their presence in the Southern Caribbean has been scarcely recorded up to date. An unusual sighting of a killer whale is described for the first time in inshore waters of the Gulf of Morrosquillo. The whale was sighted on 22 March 2015 and it was a solitary individual of unrecognized sex that showed ongoing diving and surfacing behavior at a site 6.3 km from the coast with depths between 20 and 24 m. Its occurrence could be related to favorable environmental and oceanographic conditions and to the potential effect of recent seismic offshore oil and gas operations in the gulf, which may impact a whale’s location and behavior. This report contributes to the scarcity of information about the distribution of O. orca in the Caribbean Sea along the coast of Colombia.