Baseball cap This article needs more sources for reliability. Please help improve this article by adding reliable sources. Unsourced material may be challenged or removed.Find sources: "Baseball cap" – news · newspapers · books · scholar · JSTOR (February 2018) (Learn how and when to remove this template message) A baseball cap is a type of hat worn by baseball players when they play as part of their team's uniform, but other people wear them as well. This short article about sports can be made longer. You can help Wikipedia by adding to it.