Plato didn’t furnish a detailed and clear theory about evil. What one can find in some of his dialogues is just certain hints to issues like the source of evil. The obscurity of Plato’s works led to a vast controversy over his real views on the source of evil to the extent that some scholars maintain that he didn’t develop any theory in this respect. Those who think that Plato has a theory don’t agree over what Plato takes as the source of evil. In this paper, with regard to the current distinction between metaphysical, natural, and moral evils, we argue that Plato believes in a distinct source for each one of these three kinds. Metaphysical evil which only occurs in the natural world has a negative nature and stems from the fact that the natural beings as the reflections of the world of ideas lack the full perfection of the ideas. Moral evils are caused by the activity of the soul and, finally, natural evils are the effects of necessity or matter. Accordingly, we conclude that in the light of the foregoing analysis the apparently inconsistent expressions of Plato would turn out to be consistent.