The effect of zinc phenylphosphonate on the crystallization of poly(lactic acid) using differential scanning calorimetry operating in dynamical mode at various cooling rates is reported. Experimental data were analyzed using the Avrami, Tobin, and Ozawa models. It is concluded that the addition of zinc phenylphosphonate modifies the crystallization process of poly(lactic acid) (changing the value of the Avrami exponent). Various parameters such as the crystallization half-time and crystallization rate constant reflect that zinc phenylphosphonate significantly accelerates the crystallization process. The activation energy value of the crystallization of poly(lactic acid), determined by the Kissinger method, increases with the addition of zinc phenylphosphonate.