In this article, we will deal with Wittgenstein’s view concerning the nature of mental states. As we know, Wittgenstein's position in this respect has been regarded by some of his commentators as something like behaviorism. In order to assess their claims, we will first turn to behaviorism in modern psychology as well as philosophical behaviorism, and then state Wittgenstein's own position about behaviorism by emphasizing on the point that, on Wittgenstein's view, "mental phenomena are neither reducible to, nor totally separable from, their bodily and behavioral expressions."