Fertilization, a critical step in animal reproduction, is triggered by a series of specialized sperm-egg interactions. However, the molecular mechanisms underlying fertilization are not well understood. Here, we identify a sperm-enriched C. elegans TRPC homolog, TRP-3. Mutations in trp-3 lead to sterility in both hermaphrodites and males due to a defect in their sperm. trp-3 mutant sperm are motile, but fail to fertilize oocytes after gamete contact. TRP-3 is initially localized in intracellular vesicles, and then translocates to the plasma membrane during sperm activation. This translocation coincides with a marked increase in store-operated calcium entry, providing an in vivo mechanism for the regulation of TRP-3 activity. As C. elegans oocytes lack egg coats, our data suggest that some TRPC family channels might function to mediate calcium influx during sperm-egg plasma membrane interactions leading to fertilization.