"The Mighty Atom" is named the worst episode of "Thunderbirds" by "TV Zone" magazine. Commenting that "for the first half of the episode we're left wondering where International Rescue is", the review also notes the ineptitude of the Hood and criticises the episode's "lazy" writing, point out that the villain's plans are thwarted by nothing more than Penelope's fear of mice. Tom Fox of "Starburst" magazine is more positive, arguing that the episode contains "plenty of curious aspects" to compensate for the Hood's "outlandish" plans; he gives a rating of three out of five.