<p>This study investigates the non-isothermal crystallization kinetics of polylactic acid (PLA), PLA/kenaf fiber (KF), and glycidyl methacrylate grafted polylactic acid (PLA-g-GMA)/KF biocomposites. Non-isothermal crystallization kinetics were analyzed with DSC, and crystallization morphologies were observed with POM. The Avrami, Ozawa, and Mo models described the non-isothermal crystallization kinetics. Determination of the half-time of crystallization (<i>t</i>_1/2) and Avrami-Jeziorny crystallization rate constant (<i>Z</i>_c) revealed that PLA/KF biocomposite reduced crystallization times across overall cooling rates and increased crystallization rates, indicating KF’s role as a nucleating agent. However, the crystallization rates of PLA/KF were hindered by the introduction of the PLA-g-GMA matrix. The Kissinger and Friedmann models agreed that activation energy (Δ<i>E</i>) for PLA/KF exhibited the lowest value, suggesting that KF accelerates the crystallization rate of PLA. Conversely, PLA-g-GMA/KF biocomposites exhibited the highest Δ<i>E</i>, providing direct kinetic evidence that the grafted GMA creates strong interfacial interactions with KF, which effectively restricts PLA chain mobility and dominates over the nucleating ability of the fiber. POM observations confirmed that KF promoted heterogeneous nucleation on PLA, while PLA-g-GMA inhibited crystallization by restricting PLA chain mobility.</p>