In the present work, we have investigated the structural response of transition metal double perovskite oxide Nd2CoFeO6 under pressure by XRD and Raman spectroscopic measurements. From XRD data, we have observed a pressure-induced structural transition from the orthorhombic phase to the monoclinic phase at about 14.8 GPa. An anomalous increase in compressibility at a much lower pressure (∼1.1 GPa) is seen where no structural transition occurs. At about the same pressure, a sudden drop in the slope of the Raman shift is observed. Further investigation at low temperatures reveals that the B1g Raman mode is strongly affected by magnetic interactions. Additional high-pressure Raman experiments with the application of a magnetic field have indicated that the mentioned anomaly around 1.1 GPa can be explained by a high-spin to low-spin transition of Co3+.