Polo hats, despite the name, are used in a variety of sports, such as golf, and as a non-athletic fashion accessory. If you wear your polo hat often, especially for sports or dirty activities such as outdoor gardening, it's inevitable the hat will need washing at some point. While you can wash the hat by hand, it's time consuming and usually less effective than throwing it in the laundry. The main concern with the laundry is helping the hat keep its shape. Accomplish this by using a washable hat mold, or maintain the hat's shape as it dries.
Place the hat in a washable hat mold, if desired. Shaped like the hat, the mold snaps around it to keep the hat in the correct form during the wash cycle.
Launder the hat alone on the gentle cycle, using about a tablespoon of gentle laundry detergent. Use a color-safe detergent if your hat is a vibrant color or you're worried about colors running. Set the cycle for warm water, not hot.
Set the hat out to air dry; never put it in the dryer.
Keep the hat in the mold as it dries. If not using a mold, set the hat out to dry shaped in its form. Use crumbled balls of newspaper stuffed inside the cap to help the hat dry in its regular shape.