  Double perovskite oxide materials have garnered tremendous interest due to
their strong spin-lattice-charge coupling. Interesting in their own right,
rare-earth-based DPOs have yet to be subjected to high-pressure studies. In
this paper, we have investigated the structural response of Nd$_2$CoFeO$_6$ to
pressure by XRD and Raman spectroscopic measurements. From XRD data, we have
observed pressure-induced structural transition from the orthorhombic phase to
the monoclinic phase at about 13.8~\si{\giga\pascal}. An anomalous increase in
compressibility at a much lower pressure($\sim$1.1~\si{\giga\pascal}) is seen
where no structural transition occurs. At about the same pressure, a sudden
drop in the slope of Raman modes is observed. Further investigation at low
temperatures reveals that the B$_g$ Raman mode is strongly affected by magnetic
interactions. Additional high-pressure Raman experiments with the application
of a magnetic field indicated that the mentioned anomaly around
1.1~\si{\giga\pascal} can be explained by a high-spin to low-spin transition of
Co$^{3+}$.
