Abstract The effects of oxygen vacancy on the critical magnetic behavior in La0.4Ca0.6MnO2.8□0.2 around the paramagnetic-ferromagnetic (PM-FM) phase transition were investigated through various techniques such as modified Arrott plot, Kouvel-Fisher method and critical isotherm analysis via dc magnetization measurements recorded around the Curie temperature TC. The obtained critical exponents values are β∼0.8, γ∼0.7 and δ∼1.882 with TC∼164.5 K. Thus the scaling law γ+β=δβ is fulfilled. The critical exponents obey the single scaling-equation of state M ( H , e ) | e | − β = f ± ( H | e | − ( β + γ ) ) where, f+ for T>TC and f- for T>TC. The found exponents are inconsistent with any known universality class. These results attributed to the existence of Griffiths Phase (Triki et al. (2012) [1] ) seem to actually reflect the unconventional critical scaling of the magnetic susceptibility.