Trichomycterus poikilos is a species of pencil catfish endemic to Brazil, where it occurs in the Jacuí, Pardo and Taquari-das Antas river basins, tributaries of the Laguna dos Patos system, in the state of Rio Grande do Sul.

This species reaches a maximum length of 9.25 centimetres (3.64 in) SL.

[1] The specific name poikilos is derived from the Greek adjective ποικίλος, meaning variegated, varicolored, and refers to the intraspecific color pattern variation of the species.

[1] The species' type locality (municipality of Júlio de Castilhos, arroio Passo dos Buracos, upper Jacuí river basin) is a rapid flow river with clear water, a rocky bottom and submerged vegetation, located at approximately 405 m a.s.l.

[1] T. poikilos feeds on aquatic larvae of Diptera (Simuliidae) and Lepidoptera and nymphs of the Ephemeroptera and Plecoptera.