Bring your wedding dress to a well-ventilated area such as outdoors. Put on a mask to avoid inhaling the spores from the mildew. Use a brush to remove as much mildew from the dress as possible.
Check the label inside the wedding dress to determine if it is safe to use chlorine bleach. If it is safe, mix 2 tablespoons of chlorine bleach with 1 quart of warm water. Use a sponge to apply the bleach solution to the mildew or you can submerge the dress in the water. Leave the bleach solution on the mildew stain for five to 15 minutes. Rinse and dry the dress immediately.
Apply lemon juice and salt to the mildew stain if bleach cannot be used. Moisten the mildew stain with 1 teaspoon of lemon juice and sprinkle a pinch of salt over the mildew. Put the wedding dress in the sun for at least 10 minutes. Rinse the dress.