[3] In August 1916, N. klossii was formally described by Henry Nicholas Ridley in a report on the Wollaston Expedition published in The Transactions of the Linnean Society of London.

The operculum is of a deep purple, the colour of the rest I do not know.A revised description[note a] and illustration of N. klossii were published in 1928 in B. H. Danser's seminal monograph "The Nepenthaceae of the Netherlands Indies".

[5][6] With regards to the intrageneric relationships of N. klossii, Danser wrote: "This insufficiently described species seems to be closely related to N. stenophylla, but I dare not unite these two."

It has an obtuse apex and is abruptly contracted towards the petiole, which is up to 6 cm long and bears a pair of wings (≤5 mm wide).

The glandular region is composed of tiny overarched glands and covers the lower half of the pitcher's inner surface.

An obtuse, laterally-flattened appendage (≤8 mm long) is present in the basal part of the midrib on the lid's lower surface.

Both the appendage and the lower surface of the lid are wholly glandular, bearing numerous deepened and rimmed glands of varying sizes.

An unbranched, attenuate spur is inserted on the highest part of the pitcher's dome, around 20 mm from the base of the lid.

The only easily accessible population of N. klossii is threatened by a road planned to run through its habitat, the construction of which had already begun as of March 2009.

[9][16] Nepenthes klossii is one of only two species in the genus to employ domed pitchers with white patches that allow sunlight to illuminate their interiors.

[17] Although there has been no comprehensive study of the trapping mechanism of N. klossii, it has been suggested that in the upper pitchers of N. aristolochioides this adaptation serves to attract flying insects in a similar manner to the North American pitcher plants Darlingtonia californica, Sarracenia minor, and Sarracenia psittacina.

Most of the prey caught by N. aristolochioides and N. klossii consists of small flying insects, which are attracted to bright light sources.

[18] The unique adaptations of these taxa are thought to represent an example of convergent evolution, whereby two organisms that are not closely related independently acquire similar characteristics while evolving in separate, but comparable, ecosystems.

[9] Nepenthes eustachya from Sumatra exhibits considerable variability and occasionally produces hooded upper pitchers that superficially resemble those of N. klossii.

; ascidia rosularum et inferiora ignota ; ascidia superiora magna, anguste infundibuliformia, costis 2 prominentibus ; peristomio operculum versus in collum breve elongato, applanato, 2-5 mm lato, costis c. 1/2-1/3 mm distantibus, dentibus fere 0 ; operculo suborbiculari basi cordato, facie inferiore prope basin appendice lateraliter applanata ; inflorescentia racemus pedicellis inferioribus c. 10 mm longis, 1- 3-floris ; indumentum villosum, e pilis stellatis brevibus, ramosis longioribus et simplicibus longissimis compositum.