Tantilla tjiasmantoi is a species of snake in the subfamily Colubrinae of the family Colubridae. The species is endemic to Peru.
Large for its genus, Tantilla tjiasmantoi may attain a snout-to-vent length (SVL) of and a total length (tail included) of . Unusual for its genus, T. tjiasmantoi has a dorsal color pattern of crossbars, unlike most of its congeners which are striped.
The specific name, tjiasmantoi, is in honor of of Indonesia in recognition of his support of nature conservation and taxonomic research through the BIOPAT initiative.
Tantilla tjiasmantoi is found in Department of La Libertad, Peru.
The preferred natural habitat of Tantilla tjiasmantoi is forest, at altitudes of .
Tantilla tjiasmantoi is oviparous.