An anime adaptation of Sword Art Online was announced at Dengeki Bunko Autumn

An anime adaptation of Sword Art Online was announced at Dengeki Bunko Autumn Festival 2011, along with Reki Kawahara's other light novel series, Accel World.[31] The anime is produced by Aniplex, animated by A-1 Pictures and directed by Tomohiko Ito with music by Yuki Kajiura.[32] The anime aired on Tokyo MX, tvk, TVS, TVA, RKB, HBC and MBS between July 7 and December 22, 2012, and on AT-X, Chiba TV and BS11 at later dates.[33] The Cosplay Costumes series was also streamed on Crunchyroll and Hulu.[34] The anime is adapted from the first four novels and parts of volume eight. The opening theme song for the first 14 episodes is "Crossing Field" by LiSA[35] and the ending theme song is "Yume Sekai" (ユメセカイ?, lit. "Dream World") by Haruka Tomatsu.[36] From episode 15 onward, the opening theme is "Innocence" by Eir Aoi and the ending theme is "Overfly" by Luna Haruna.

The anime has been licensed in North America by Aniplex of America[37] and an English-language dub premiered on Adult Swim's Toonami from July 27, 2013[38] to February 15, 2014. The series was released by Aniplex of America in four DVD and Blu-ray sets, with special extras on the BD sets, between August 13 and November 19, 2013.[39] Manga Entertainment Sword Art Online Costumes released the first series on BD/DVD in the United Kingdom in December 2013,[40] whilst Madman Entertainment released the series in Australia[41] and the English-language version began airing on ABC3 on June 7, 2014.[42] Sword Art Online has been available on Netflix in North America since March 15, 2014.[43]

A year-end special, titled Sword Art Online Extra Edition, aired on December 31, 2013. The special recapped the previously aired anime series and included some new footage.[44] The special's main theme is "Niji no Oto" (虹の音 Sound of the Rainbow?) by Eir Aoi.[45] Extra Edition was streamed worldwide a few hours after its airing in Japan.[46] The two-hour-long special was available on Daisuki worldwide except for French-speaking areas, Cosplay Costumes as well as China and Korea.[46] Daisuki offered subtitles in various languages such as English, Spanish, Portuguese, Italian, and German.[46] English-speaking countries, Mexico, Central and South America could also watch the stream on Crunchyroll.[47] Extra Edition was also simulcast in Korea on Aniplus cable channel and in China on the LeTV streaming website.[47] French-speaking countries could watch on the Wakanim streaming website.[47] The Blu-ray Disc and DVD of Extra Edition was released on April 23, 2014 in Japan.[48] The limited edition included a Yui character song titled "Heart Sweet Heart" by Kanae Itō and an original side story written by Reki Kawahara titled "Sword Art Online Niji no Hashi" (ソードアート・オンライン 虹の橋 Sword Art Online Rainbow Bridge?).