Vacuum fluctuations provide an important new way to control material properties noninvasively1-6. Here, we present experimental evidence that they can enhance superconductivity. NbSe2 is a layered transition-metal dichalcogenide with well-characterized superconducting behavior, providing a clear platform to reveal this effect. We have observed an increase in the critical temperature of superconducting NbSe2 when it is embedded in a split-ring cavity resonator. Near the transition temperature, the critical current and critical field increase dramatically. Our observations are consistent with theoretical calculations showing that hybridization between electronic degrees of freedom and fluctuating cavity modes lowers the energy of the superconducting state. By providing a proof-of-principle demonstration of superconductivity enhancement via vacuum fluctuations, our work establishes a noninvasive technique for controlling the mainstay of quantum technology.