Devastated over losing his only child in a car accident, Dr. Umatarou Tenma, the director of the Ministry of Science, mobilizes the institution's entire staff to create Atom: an ultimate technology robot made in his late son Tobio's exact image. Aside from unmatched power and intelligence, the robot also possesses the innocence and playfulness of a young boy.

However, Atom fails to meet Tenma's expectations when the latter realizes that Tobio's replacement cannot grow. Unable to recognize Atom for what he is, Tenma wishes to forget the whole affair. Dismissing the feelings of what he considers just a machine, he cruelly sells the android to a robot circus that treats its performers as merely disposable tools. Despite his predicament, Atom shows kindness to his wretched kin and humans alike, sparing no effort in times of crisis to keep everyone safe.

Soon, fortune smiles on the mechanical boy, as Dr. Ochanomizu—a visionary who fights against the abuse of robots—frees him from the circus. Under Ochanomizu's guidance and with a chance to forge a path in their mixed human-robot society, Atom fights tirelessly to make the world a peaceful place while also discovering its vast complexity.

Tetsuwan Atom was the first television anime series to air in a 30-minute programming slot. It was broadcast by Fuji Television and reached over 40 percent viewership rating by the following year. The February 2004 issue of the Cinefantastique American magazine listed it as one of the 10 Essential Anime. It ranked second in the 100 Select Works of Media Arts survey for the animation category, which was held in 2006 by the Japan Media Arts Festival. The series also won several awards: the Special Award at the second Television Reporters Conference in 1964, The Ministry of Health and Welfare Award in 1965, and the Galaxy Award at the fourth Broadcast Critics' Discussion in 1967.

When television producer Fred Ladd helped NBC Enterprises adapt the series for broadcast in the United States in 1963, the title Astro Boy was used instead of the manga's English title Mighty Atom. Only the first 104 episodes were made available in English and aired in an alternative order, with adjustments for the American audience.

In North America, Right Stuf International released several VHS tapes of the series between 1989 and 1995; the company returned with all 104 episodes on DVD—as a collection of two 11-disc sets—from March 27, 2006, to August 29, 2006. A subsequent mini collection of two five-disc sets and an independent five-episode DVD Astro Boy: The Beginning also became available on October 6, 2009.