Nepenthes mantalingajanensis was first collected on Mount Mantalingajan in 1992, during a botanical expedition to the summit of the mountain by botanists G. C. G. Argent and E. M. Romero. The specimen, G.C.G.Argent & E.M.Romero 92114, was taken on March 2, 1992, at an altitude of 1700 m, and is deposited at the Kew Herbarium (K) in London.
The species entered cultivation in 1998, prior to receiving a formal description; plants in cultivation were generally referred to as Nepenthes spec. Palawan 1. Nepenthes mantalingajanensis was formally described by Joachim Nerz and Andreas Wistuba in a 2007 issue of Das Taublatt. The herbarium specimen J.Nerz & A.Wistuba P001 is the designated holotype, and is deposited at the herbarium of the Institut für Biologie I at the Eberhard Karls University of Tübingen (TUB).
Depending on environmental conditions, N. mantalingajanensis may grow as a compact rosette or produce an upright stem 30–60 cm tall. Internodes are circular in cross section and up to 1 cm in diameter. The species does not appear to produce a climbing stem.
Leaves are petiolate to sub-petiolate and coriaceous in texture. The lamina (leaf blade) is broadly lanceolate in shape and can reach 20 cm in length by 6 cm in width. The apex of the lamina is typically acute or obtuse, but may be sub-peltate, with the point of tendril attachment being up to 4 mm from the apex. The lamina is attenuate at its base. The petiole itself is amplexicaul, canaliculate (grooved lengthwise), and up to 7 cm long. Tendrils are up to 30 cm long.
Rosette and lower pitchers are usually ovate or obconic, although ones that develop embedded in substrate often have a more globose shape. Pitchers produced on older plants are generally more elongated with a narrower basal portion. Terrestrial pitchers are quite small, typically reaching only 15 cm in height by 6.5 cm in width, although particularly globose traps may be 12 cm wide. A pair of wings (≤8 mm wide), with fringe elements up to 5 mm long, usually runs down the ventral surface of the pitcher cup, although the wings may occasionally be reduced to ribs. The peristome is approximately cylindrical and up to 2 cm across. It bears ribs up to 2 mm high and spaced up to 3 mm apart, which terminate in curved teeth up to 5 mm long. The peristome is elongated into a neck at the rear, where the teeth on the two lobes of the peristome run apart to form distinctive gap. The pitcher lid or operculum is cordate (heart-shaped) and may have a rounded or pointed tip. It measures up to 5 cm in length by 4 cm in width and does not bear any appendages. The spur, which is inserted near the base of the lid, is up to 8 mm long and may be simple or branched.