Vaglio Serra (Vaj in Piedmontese language) is a comune (municipality) in the Province of Asti in the Italian region Piedmont, located about southeast of Turin and about southeast of Asti, measured in a straight line. As of 31 December 2004, it had a population of 293 and an area of .
Vaglio Serra borders the following municipalities: Cortiglione, Incisa Scapaccino, Nizza Monferrato, and Vinchio. It is part of the UNESCO World Heritage Site https://www.paesaggivitivinicoliunesco.it/patrimonio/nizza-monferrato-e-il-barbera/