Abstract: The electroweak sphaleron process breaks the baryon number conservation within the realms of the Standard Model of particle physics. Recently, it was pointed out that its decoupling may provide the out-of-equilibrium condition required for baryogenesis. In this paper, we study such a scenario taking into account the baryon-number wash-out effect of the sphaleron itself to improve the estimate. We clarify the amount of $CP$ violation required for this scenario to explain the observed asymmetry.