Nepenthes robcantleyi was first collected from a single site at Mt Pasian in the Pacific Cordillera mountain range of E Mindanao, then being logged, in 1997. Robert Cantley, the collector, revisited the locality twice in the following two years without success, indicating it may have been locally extirpated (Cheek 2011). Subsequently it was discovered on Mt Mayo at the southern end of the same group of mountains (Cheek 2015, Smith 2015). However, plants at the Mt Mayo site together with those at Mt Candalaga (fide A. Robinson 2015) were later published as the new species N. nebularum in 2016 (Mansell and Suarez 2016). Furthermore, Mansell and Suarez (2017) later claimed that N. robcantleyi was likely a hybrid between N. nebularum and N. truncata. The original publication, however, went to some length to explain the reasons that such an interpretation is unlikely, particularly in light of its breeding true for two generations (Cheek 2011). Since the name N. robcantleyi holds historic precedence, and as the hybrid nature of N. robcantleyi has not been demonstrated, the concept of the original publication (Cheek 2011) is adopted in this assessment. 

Nepenthes robcantleyi is widely cultivated by enthusiasts for its spectacular pitchers and much used as a parent of vigorous, colourful, commercial horticultural hybrids. In the wild it is usually an epiphyte of cloud forest and is often (always) found growing with the similarly large N. truncata. The two species have a different flowering time (Cheek 2011).

The author of N. robcantleyi (Cheek 2011) originally indicated this species was known from a single locality, at Mt Pasian, which had apparently been cleared of its forest habitat for timber. Therefore this species was considered Extinct in the Wild, or at the very least Critically Endangered. However, since then, additional localities have been reported (e.g. Cheek 2015, Smith 2015; Amoroso and Lagunday pers. comm. to Cheek 2024, A. Robinson pers. comm. 2024). It is clear that this species has a small range with several points within the mountains of southeastern Mindanao. However, there is controversy associated with this species, seemingly connected with commercial rivalry in the Nepenthes horticultural hybrid world where N. robcantleyi has become popular as a parent of hybrid cultivars. The additional locations have been considered as a separate species, N. nebularum (Mansell and Suarez 2016) but taxonomic experts consider the latter to be a synonym and this is the view taken in this assessment (see Taxonomic Note). Based on the available information, the number of locations is considered to be four, and the extent of occurrence (EOO) is calculated as 2,085 km² and the area of occupancy (AOO) is 16 km². The species is suspected to be present at several currently unnamed localities and so the AOO and EOO should be considered lower-bound values. However, the true AOO and EOO are still highly likely to fall comfortably within the thresholds for an Endangered assessment under criterion B, as the species is likely to be confined to the same SE range of Mindanao.

It is not possible to provide an accurate estimate of the population size at present, but it can be inferred that the population is in decline given the reported massive poaching of plants. Based on the available information the species is assessed as Endangered (EN) under  criteria B1ab(iii,iv,v)+2ab(iii,iv,v).

This species is known from a small region in eastern Mindanao, Philippines. There are currently five known localities for the species, with one of these five considered possibly extinct due to extensive logging in the area. It has been suggested that the species is known from several other, unnamed localities (A. Robinson pers. comm. 2024).

The population size of this species cannot be estimated until detailed field studies are conducted on this species.

The species grows as an epiphytic shrub in montane forests, up to an altitude of approximately 1,800 m.

This species faces multiple threats, including land clearing for agriculture/logging of the trees on which it grows, and possibly also collection of plants for trade. There have been massive poaching events in recent years at several localities (A. Robinson pers. comm. 2024).

The species is in cultivation and is keenly sought by enthusiasts of Nepenthes for its large, richly coloured pitchers. Cultivated plants are sold online to collectors. It has no other known uses or value apart from making hybrid plants for cultivation.

This species is currently listed in CITES Appendix II as are all species apart from those on Appendix I, but is not subject to any other direct conservation actions. There is an urgent need to survey this species in the field to more accurately determine its population size, AOO and EOO, as well as threats and appropriate conservation actions.