This work describes the effect of the laser power and the exposure time on a sample of octahedron‐shaped nanocrystals of cobalt(II) oxide using Raman spectroscopy. Above a certain value of the laser power and exposure time, CoO rock salt sample evolves clearly to the oxidized Co3O4 normal spinel material because of the energy transfer and consequent local heating induced by the applied laser. The analysis of this thermodynamic CoO–Co3O4 crossover in octahedron‐shaped nanocrystals by means of the Raman spectroscopy has been performed. Copyright © 2017 John Wiley & Sons, Ltd. The thermodynamic crossover of octahedron‐shaped nanocrystals of cobalt(II) oxide to oxidized Co3O4 normal spinel is studied using Raman spectroscopy. For that, the effect of the laser power from 0.3 (0.05%) to 69 (100%) mW and of the exposure time using different laser wavelengths was analyzed. Controlling both laser power and time exposure, the sample evolution from CoO rock salt to Co3O4 fcc spinel was attained, stemming from the energy transfer and consequent local heating.