Because the manga was still ongoing during production, author Hiromu Arakawa asked Bones to create an original ending different from the manga rather than repeat the same conclusion in both media, so she could keep developing the manga at her own pace.

Bones president Masahiko Minami decided to adapt Fullmetal Alchemist after staffers including Yoshiyuki Ito brought the manga to his attention, and the studio then secured a deal with Arakawa and publisher Square Enix to produce the anime.

Although Arakawa let Bones work independently and did not write for the TV series, she was present in meetings to advise the staff on the world of Fullmetal Alchemist and helped fill in gaps for the anime's original ending, as shown in extras of Volume 8 of the manga.

Because Arakawa was involved in advising the anime's development, she had little time left to focus on illustrating the manga's cover illustrations during that period.

Actress Miho Shiraishi made her voice-acting debut in episode 10, 'The Phantom Thief Siren,' voicing Clara/Siren, which drew attention from entertainment media.

The score was composed and arranged by Michiru Ōshima and recorded at Mosfilm in Russia by the Moscow Symphony Orchestra, an arrangement set up by Russian Japanologist-turned-cosmetics businesswoman Tatiana Naumova.

The Russian-language theme song 'Brothers' (Братья), with lyrics written by director Seiji Mizushima and translated into Russian by Naumova, became the signature song of the 2003 series precisely because it was left out of the 2009 Brotherhood remake; Vic Mignogna recorded an English version that was never officially released.

The compilation album 'Fullmetal Alchemist Complete Best,' gathering all opening and ending themes, debuted at number one on the Oricon albums chart, making it only the fourth anime CD ever to top the chart and the first anime compilation album to do so.

The title 'Fullmetal Alchemist' in English was deliberately not used for the original Japanese-language branding of this 2003 series in Japan, in order to distinguish it from the 2009 remake officially titled 'Fullmetal Alchemist: Brotherhood' in Japan.

The series won 'Best Long Series,' 'Best DVD Package Design,' and 'Best Casting' at the American Anime Awards, with Vic Mignogna winning 'Best Actor' for voicing Edward Elric and 'Rewrite' by Asian Kung-Fu Generation winning 'Best Theme Song.'

In both 2005 and 2006, Japanese network TV Asahi's 'Top 100 anime' online polls ranked Fullmetal Alchemist number one.

Later critics such as Piotr Konieczny and Paste's Juan Barquin praised the original 2003 series for its darker tone and more tragic ending compared to Brotherhood, and some, like Daniel Schindel of Polygon, considered its messier, more idiosyncratic execution ultimately more beautiful and impactful despite being less faithful to the source manga.