A vehicle body structure includes a cowl extending in a vehicle transverse direction at an upper rear section of an engine compartment, an air inlet to introduce outside air into a vehicle cabin from the cowl, a fluid discharge channel provided at the bottom of the cowl, the fluid discharge channel inclined to guide fluid entering the cowl to a drain opening disposed at a transverse end of the cowl, a one-way valve disposed inside the cowl at a position corresponding to the drain opening, the one-way valve including a flapper operable to open and close the drain opening in response to a differential pressure generated when air flows through the air inlet and a frame comprising a valve opening corresponding to the drain opening, wherein the one-way valve covers the drain opening.