The second season of the Japanese animated television series A Certain Magical Index, marketed as A Certain Magical Index II, is based on the light novel series of the same name written by Kazuma Kamachi and illustrated by Kiyotaka Haimura. The season follows the adventures of Toma Kamijo and Index as they face the threat of the Roman Catholic Church. Produced by J.C.Staff, the season saw Hiroshi Nishikiori and Masanao Akahoshi [ja] respectively serving as director and series composition writer.

Atsushi Abe and Yuka Iguchi reprise their respective roles as the lead characters Kamijo and Index. The returning cast also includes Rina Satō, Shizuka Itō, Kishō Taniyama, Anri Katsu [ja], Kimiko Koyama, Satomi Arai, and Nobuhiko Okamoto. The second season was confirmed in June 2010 and adapts from the seventh to the thirteenth volume of the light novel.

The second season consists of 24 episodes and ran on AT-X from October 8, 2010, to April 1, 2011, with other networks following days later. A third season was announced in October 2017 as part of the "A Certain Project 2018" event.

The production for A Certain Magical Index II was greenlit in June 2010. J.C.Staff returned to produce the series, while Hiroshi Nishikiori, Masanao Akahoshi, and Yuichi Tanaka reunited from the previous season to serve as the director, series composition writer, and character animation designer, respectively. The second season adapted the seventh to the thirteenth volume of A Certain Magical Index light novel series. Yuka Iguchi revealed that Nishikiori instructed her to act "like a big shot with no proof" during recording. Rina Satō also revealed that the staff told her about Mikoto Misaka, her character, falling in love with Toma Kamijo in the second season but felt that their current rivalry was the "best way to go". Kishō Taniyama enjoyed Stiyl Magnus' teasing and tsundere-like nature, and noted that his character was "unbearable". Nozomi Sasaki revealed how she was told to bring out Misaka 10032's "individual differences" among the Misaka clones for the second season, which she found difficult to do since she eliminated it in the first season.

In June 2010, Atsushi Abe, Iguchi, and Satō were set to reprise their respective roles as Kamijo, Index, and Misaka. Shizuka Itō, Taniyama, Anri Katsu, Kimiko Koyama, and Nobuhiko Okamoto also reprise their respective roles as Kaori Kanzaki, Magnus, Motoharu Tsuchimikado, Komoe Tsukuyomi, and Accelerator. In September 2010, four new characters belonging to the Roman Catholic Church would be introduced in the series. They are Orsola Aquinas, voiced by Aya Endō, Agnese Sanctis, voiced by Rie Kugimiya, Lucia, voiced by Mariya Ise, and Angelene, voiced by Azusa Enoki.

In July 2014, Funimation announced the English dub cast for the new characters that appeared in the series. These include Mallorie Rodak as Aquinas, Alex Moore as Sanctis, Lauren Landa as Lucia, Kristin Sutton as Angelene, Duncan Brannan as Saiji Tatemiya, Bryn Apprill as Awaki Musujime, Jennifer Green as Oriana Thomson, Rachel Robinson as Lidvia Lorenzetti, and Skyler McIntosh as Seiri Fukiyose. By the following month, Kara Edwards and Marcus Stimac joined the cast as Vento of the Front and Amata Kihara, respectively.

Maiko Iuchi of I've Sound returned to compose the second season, after previously doing so for A Certain Magical Index (2008). The opening theme music that aired from episodes 1 to 16 is "No Buts!" by Mami Kawada and was released on November 3, 2010. The first ending theme music that aired from episodes 1 to 13 is "Magic∞World" by Maon Kurosaki and was released on November 24, 2010. The second opening theme music that aired from episodes 17 onwards is "See Visions" by Kawada and was released on February 16, 2011. The second ending theme music that aired from episode 14 onwards is "Memories Last" (メモリーズ・ラスト, Memorīzu・Rasuto) by Kurosaki and was released on March 2, 2011.

In September 2010, a 15-second commercial video and two collaborative commercial videos, narrated by Oreimo characters Kirino Kosaka and Kyōsuke Kosaka, for A Certain Magical Index II were released. The series also held collaboration with Maid Sama! In the same month, the edited version of the series' first episode ("August 31st") was screened at Dengeki Bungko Autumn Festival 2010. Abe, Iguchi, Satō, Itō, Taniyama, and producer Nobuhiro Nakayama were also present at the event to promote the series.