This paper reports selective acetone sensing portrayed by functionalized nano-porous silicon (PS). Functionalization of nanostructure was performed using hexamethyldisilazane (HMDS). Nano-PS fabrication and morphology analysis were done using electrochemical etching and SEM respectively. Optical properties of PS were analyzed using Raman and Photoluminescence (PL) spectroscopy. Parallel aluminium electrodes were formed on nano-PS surface using thermal evaporation technique. These electrodes were used for recording electrical measurements from porous surface in presence of volatile organic compounds (VOCs) and moisture. Resistance variations due to interaction of sensing surface with different concentrations of ethanol, acetone, moisture and isopropyl alcohol vapors were monitored at room temperature. Various sensor parameters were calculated like sensitivity, response- and recovery-time. Sensor based on functionalized nano-PS was found to be most responsive for acetone in comparison to other VOCs or moisture. Since, acetone is one of the important metabolite components in the circulated blood of the human body therefore, its concentration determination is necessary. The approach for selective sensing presented in this work is simple and low cost. © 2015 IEEE.