Dir en grey's format has been subject to change throughout their career, initially being a rather experimental form of alternative rock. Some tracks of their debut album Gauze also demonstrated a distinct pop appeal, which was largely dropped in favor of a more progressive sound on the following albums, Macabre and Kisou. While up to that point some songs had already been more fast-paced, raw and aggressive than others, the band's music took a decisive turn with the release of the EP Six Ugly, from then on sporting more metal influences in general. Dir en grey's style has since gravitated towards riffs and song structures more along the lines of contemporary North American fusion genres, such as nu metal and metalcore, though their latest album, Uroboros, sees them return to the more experimental and oriental sound of their earlier albums. Since its release many sources have begun classifying Dir en grey as progressive metal. In a review of their sixth full length album, The Marrow of a Bone, allmusic comments on their evolution and diversity, saying:

“     The band's sound has embraced tendencies of American metal and nu metal (they participated in Korn's Family Values tour in America), and Dir en Grey bring so many other sonic and musical elements into the mix that they extend not only the reach of their own music, but the boundaries of any music they happen to incorporate into their sound.     ”

— Thom Jurek, Allmusic


Kyo's singing is considered a pivotal aspect of the band, and he has gained recognition for his distinctive vocal work and for his large range and versatility, being able to "howl, croon, emote cleanly, scream, shriek, growl, bellow, and make nearly inhuman sounds", and he has been compared favorably to singer and avant garde musician Mike Patton. In their review of Uroboros, Sputnik Music says only of Kyo's singing, "I challenge you to find one singer in any genre with more range than this guy". All lyrics are written by Kyo and deal with subjects such as society, mass media as well as sexual obsessions and love, usually with negative implications. The vocabulary varies from subtle to explicit and several songs rely heavily on double entendres and other wordplay, often involving the multiple meanings of a kanji character.