Key message <p>The rice pollen-specific calmodulin–like protein OsCML17 contributes to fertilization by regulating pollen germination and pollen tube elongation, and is localized to the endoplasmic reticulum and plasma membrane.</p> Abstract <p>In angiosperms, successful fertilization relies on the precise growth of the pollen tube growth. Calcium ion (Ca²⁺) regulates various physiological responses and plays a critical role in pollen germination and pollen tube growth. Calmodulin–like proteins (CMLs), which consist of EF-hand motifs, function as Ca²⁺ sensors that detect changes in intracellular Ca²⁺ concentrations and regulate specific signaling pathways. Despite their significance, the expression dynamics and functional significance of <i>CML</i>s in rice remain largely unexplored. In this study, we examined expression profiles and structural properties of 32 <i>CML</i> genes in rice to identify those preferentially expressed in pollen. <i>OsCML17</i> exhibited strong expression in rice mature anthers containing tricellular pollen and was localized to both the endoplasmic reticulum and the plasma membrane in the tobacco cells. Knockout mutants of <i>OsCML17</i> generated by CRISPR/Cas9 exhibited consistently reduced pollen germination rates and shorter pollen tubes. Moreover, the <i>OsCML17</i> transcript was markedly decreased in the mature pollen of the <i>madstri</i> mutant, indicating potential transcriptional regulation by MADS–box factors. Overall, these findings suggest that <i>OsCML17</i> functions as an important factor regulating pollen germination and tube elongation in rice.</p>