An air permeable cap for a vehicle may include: a cover part formed in a cylindrical shape with a closed end part, and having a plurality of guide ribs radially formed on an inner circumferential surface thereof; a foam part inserted and installed in the cover part so as to be contacted with the guide ribs, and having a ventilation hole formed on one side thereof; a membrane part installed between the foam part and the cover part, and configured to block a flow of water through the ventilation hole and allow a flow of air through the ventilation hole; and an adhesion retention part coupled in a concave-convex shape to retain an adhesion force between the foam part and the cover part.