The constitutive 70 kDa heat-shock protein, HSPA8, has previously been shown to contribute to the long-term survival of spermatozoa inside the mammalian female reproductive tract. Here, we show that a recombinant form of HSPA8 rapidly promotes the viability of uncapacitated spermatozoa, the ability of spermatozoa to bind to oviductal epithelial cells, enhances IVF performance, and decreases sperm mitochondrial activity. Fluorescence recovery after photobleaching revealed that the repair of membrane damage is achieved by an almost instantaneous increase in sperm membrane fluidity. The ability of HSPA8 to influence membrane stability and fluidity, as well as its conserved nature among mammalian species, supports the idea that this protein protects sperm survival through membrane repair mechanisms. Free Persian abstract A Persian translation of the abstract is freely available online at http://www.reproduction-online.org/content/147/5/719/suppl/DC1.