While its underside is silver to white in color, its back and sides are typically noticeably blue, with numerous small dark spots.

The species is smaller than many of its congeners, reaching around 27 cm (11 in) in total length.

[1] It is believed that the blue coloration, comparatively fusiform body, smaller size, and falcate fins of D. eydouxii are adaptations to its open-water environment, distinguishing it from non-pelagic (except as juveniles) species such as Diodon hystrix.

[3] Diodon eydouxii is known from the Atlantic, Pacific, and Indian oceans, where it typically occurs in warm, tropical areas with a water temperature between 23.1 and 29.1 °C (73.6 and 84.4 °F).

[4] Diodon eydouxii is known to be a schooling species, distinguishing it from many tetraodontiform fish which are often solitary.