Much like other members of Deuterodon, and like some species in related genera like Astyanax or Jupiaba, D. oyakawai is a silvery fish with fins in some combination of red and clear.

[8] Deuterodon sazimai is a small fish, reaching a maximum of 5.7 cm (2.2 in) SL (standard length, with the tail fin left out of the measurement).

The back darkens to a brownish color because of the chromatophores concentrated in the middle and base of the scales (lacking at the margins), and the body remains pale below the lateral line.

There is a large, wedge-shaped humeral spot, and a dark lateral stripe that leads to another blotch of pigment on the caudal peduncle, shaped like a horizontal oval.

[11] Deuterodon sazimai is known to occur in the basins of the Itapemirim and Doce rivers, which are located in the Espírito Santo and Minas Gerais states of southeastern Brazil, respectively.

[12] The Doce river basin is located further north along the Atlantic coastline, and flows for about 853 km (530 mi); the ecosystem therein is considered sensitive to climate variability.

Other dietary contributors, much less prevalent than scales, have been found in the mouths of preserved specimens on occasion; these include leaf fragments and insects.