Males of Rivulus parlettei differs from males of other members of the R. limoncochae group by having irregular interrupted lines of dots wider than the interspaces (vs. longitudinal rows of dots, sometimes coalescing to form stripes narrower than the interspaces), by an inferior lip without distinctive colouration (vs. red inferior lip), a dorsal and anal fin without a dark posterior tip (vs. presence of dark tip), a light blue venter (vs. yellow in R. christinae and white in the remaining species of R. limoncochae group) and a yellowish anal fin with a whitish basal region (vs. yellow with light blue basal region). Females of R. parlettei can be diagnosed from females of the other species of the R. limoncochae by the presence of variable shaped orange spots on body sides (mainly above anal fin) forming oblique bars (vs. absence of spots or spots forming stripes), by a yellow-orange ventral parts of head, venter and caudal peduncle (vs. light blue to light brown) and by having orange to yellow paired fins (vs. yellowish hyaline or hyaline paired fins). This species can be further distinguished by the position of its dorsal-fin origin (dorsal fin origin above base of 7th or 8th of anal-fin ray ( vs. 9th or 12th anal-fin ray in R. christinae, R. erberi, R. iridescens, R. rubrolineatus, and R. taeniatus) (Ref. 88925).