Overshirts are outerwear items which are constructed like shirts and wear like jackets. They most often feature collars, front closure (buttons or zipper) and barrel cuffs from shirts, but are made with thicker, warmer materials and sometimes pockets derived from jackets.

Overshirts run the gamut from very shirt-like to appear more like a jacket, but are almost always unlined. Most of them are made of a dense weave which block more wind than a knit sweater would. It is not uncommon to see wool or technical fabrics.

Most overshirts fit a bit more generously than pure shirts in order to make room for a baselayer underneath. They are, however, nowhere near as bulky as a dedicated jacket, which is part of the appeal. As a rule you should go with your regular shirt size. You can size up one notch for an oversized look, but there is no point in sizing down. Make sure that you can fit more than just a tee underneath.