The main goal of this work is to study the critical behavior in the as-quenched and annealed NANOPERM Fe75Mo8Cu1B16 alloy in the vicinity of the critical temperature TC. The second order phase transition from ferro- to paramagnetic state was confirmed by the positive slope of Arrott plots. The critical exponents (β, γ, and δ) have been revealed using the Kouvel-Fisher method. Moreover, the Kouvel-Fisher analysis revealed the detailed Curie temperature for all investigated samples.