With complete lateral line, without infraorbital process; with mostly 7 branched dorsal-fin rays and 11 branched anal-fin rays. Danio leptos can be distinguished from other striped Danio by its slender body (body depth 25.8-27.7% SL, versus over 29.2 in most striped Danio) and a color pattern consisting in three horizontal stripes on the sides of the body, with the middle one (P stripe) deeper (about one scale deep) and more prominent that the other two (P+1 and P-1 stripes), and, anteriorly on the sides, the dark pigment organized in vertical elements, separated by thin, irregular light interspaces, which appears somewhat similar to the vertical bars in the barred Danio species. The most similar species, D. chrysotaeniatus, has 8-9 branched dorsal-fin rays and 12-13 branched anal-fin rays, and a few short, horizontal lines derived from the I-1 interspace, instead of dark blotches anteriorly on the side.