 Classical Indian philosophers do not call themselves naturalists, but different naturalistic traits are easily detectable in different schools. The validity of this claim is tied to the concept of nature admitted in different systems, which alone determines the boundary between natural and supernatural. This article, therefore, first discusses two different theories of nature and in the light of that constructs arguments for ontological naturalism, methodological naturalism and moral naturalism by drawing on the writings of classical Indian philosophers. Naturalistic traits are not uniformly present in all systems: a single system of philosophy might uphold naturalism from one perspective and non-naturalism from another. The Naiyāyikas for example, have shown marked preference for naturalism in epistemology while in linguistic theory they are staunch conventionalists; the Advaita Vedantins on the other hand, are non-naturalists in their ontology but their epistemology can be looked upon as naturalistic. A moral naturalism is shared by most Indian philosophical systems. However, in importing these labels from Western philosophy to the classical Indian philosophical systems, one needs to exercise caution because the concepts of nature, science, scientific method, etc. do not smoothly converge in the two theoretical traditions.