The category of barrel-aged beer represents a diverse range of ale and lager styles that have been aged in non-neutral wood. These beers commonly range between 7.5-10% in alcohol with further variations depending on the interpretation of the style. These beers are characterized by both wood-influenced flavors (vanillia, caramel, toast, coconut) and secondary flavors of the alcohol previously aged in the wood (bourbon, scotch whisky, sherry). The overall character of the final beer may also included acetic, lactic or Brettanomyces flavors and aromas resultant of the barrel.

A wide variety of base beer styles may be barrel-aged for an additional level of complexity, although barrel-aged versions of darker or more alcoholic styles are among the more common examples. Noteworthy examples of this style include: Goose Island Bourbon County Stout, Alltech Kentucky Bourbon Barrel Ale and Grand Rapids The Mound Maker.