In this article, the effect of temperature on the spreading behavior of a water nano-droplet on poly(methyl methacrylate) substrate is investigated. The contact angle analysis illustrates that the spreading process occurs in a stage-like manner and the increase in temperature causes a regime change from partial to total wetting. The interaction energy distributions show that there exist sites on the surface which could trap water molecules and provide a better path for other molecules to overcome the asperities. Estimations of the coefficients of self-diffusivity suggest that temperature has a major effect in the reorientation stage, which results in the formation of the interfacial layer. In the second stage of spreading, temperature affects the process by providing sufficient energy for water molecules to overcome the interactions with the substrate. Therefore, this stage is controlled by the movement of water molecules on the surface and is highly influenced by their interaction with the surface asperities, strong interaction sites, and the carbonyl groups. (c) 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 1532-1541