The CP asymmetry parameters in the decay B0(B̄0) → J/ψπ0, were described. The measurement of the CP asymmetry parameters was based on a 140 fb-1 data sample, which was accumulated at the γ(4S) resonance by the Belle detector at the KEKB asymmetric-energy e+e- collider. It was observed that one neutral B meson flavor was identified by its decay products. The results show values of the CP-violating parameters were found to be of the order of S J/ψπ o = -0.72∓0.42(stat)∓0.09(syst) and AJ/ψπ 0 = -0.01∓0.29(stat)∓0. 03(syst).