Black tea high-molecular-weight polyphenol increases the motility of sea urchin sperm by activating mitochondrial respiration. Mitochondria activation factor (MAF) is a high-molecular-weight polyphenol purified from black tea that activates mitochondrial respiration. It increased the mitochondrial membrane potential and motility of sea urchin sperm, by up to 8%, to the same extent as sperm-activating peptides (SAPs) secreted by the egg. Unlike SAPs, MAF had no effect on sperm swimming behavior, suggesting that the mechanism of sperm activation by MAF is different from that of SAPs.