Grammangis ellisii is endemic to Madagascar and is known from 39 collections (21 occurrences). One of these collections (Chase 89102) was made with no precise locality information and thus not taken into account in this assessment. This species is also known from 13 observations recorded on iNaturalist. However, because precise GPS coordinates are not available, these observations were not considered in this assessment. Fifteen collections representing nine occurrences have been made in seven protected areas, the Manongarivo Special Reserve (one occurrence, one location), the Nosy Mangabe National Park (one occurrence, one location), the Analamazaotra National Park (three occurrences, one location), the Mantadia national park (one occurrence, one location), the Vohibe forest-Ankeniheny-Zahamena Corridor (one occurrence, one location), Torotorofotsy Protected Area (one occurrence, one location), and the Tsitongambarika Natural Resources Reserve (one occurrence, one location). In addition to these officially protected sites, 20 collections representing eight occurrences have been made in the footprint of a mining project undergoing intense human pressure such as forests clearing. These former occurrences must be considered as extirpated. Grammangis ellisii is also known from one occurrence and one location made in the conservation zone surrounding the footprint and this forest should be subject to protection in the near future. One collection (one occurrence, one location) of this species has also been made in the conservation zone surrounding the footprint of a mining project undergoing intense human pressure such as forests clearing. The conservation zone should be subjected to protection in the near future. It is also known from two collections (two occurrences, two locations) made from Vohitralongo (one occurrence, one location), and from Sainte Marie (one occurrence, one location) in unprotected forests subject to selective logging, timber harvesting for small-scale subsistence, and slash-and-burn agricultural practices (tavy). We estimate that these two occurrences will be extirpated within the next ten years. Overall, this species is known from 38 collections (21 occurrences) with precise location information representing 12 existing and eight extirpated occurrences.

The extent of occurrence (EOO) of G. ellisii is estimated to be 130,598 km² (far exceeding the limits for Vulnerable status under criterion B1) whereas its area of occupancy (AOO) is estimated to be 44 km² (which falls within the limits for Endangered status under the criterion B2). These 12 existing occurrences represent a total of 10 locations (sensu IUCN 2019) with respect to the main threat, mining activities. The loss of the subpopulation in the footprint of a mining project has induced a continuous decline of the EOO, the AOO, the number of subpopulations, locations, and the number of mature individuals. Grammangis ellisii is therefore assigned a status of Vulnerable B2ab (i,ii,iii,iv,v).

Grammangis ellisii is endemic to Madagascar where it is occurs in the former provinces of Antsiranana in the Diana Region (Manongarivo), of Antananarivo in the Analamanga Region (Vohitralongo), of Toamasina in the Analanjirofo, Alaotra-Mangoro Atsinanana Regions (Nosy Mangabe, Sainte Marie, Analamazaotra, Mantadia, Moramanga, Vohibe) and of Toliara in the Anosy Region (Tsitongambarika). The species is known from the northern, western, eastern, and southeastern escarpment plateau, between 135 and 1,300 m elevation (Madagascar Catalogue 2020).

Grammangis ellisii is currently thought to be decreasing since the subpopulation in the footprint of the mining project should be considered as extirpated. The number of mature individuals of G. ellisii is not known and cannot be estimated since the species is an epiphyte growing on the trunks of trees and on moss and lichen covered trees in humid and subhumid forests.

Grammangis ellisii is an epiphytic herb occurring in evergreen humid and subhumid forests, growing on tree trunks, moss, and lichen covered trees in mossy at low to mid-elevation.

This species is mostly threatened by mining and illegal collection for horticulture. Eight occurrences of this species have been collected on the footprint of a mining project undergoing intense human pressure such as forests clearing. It is also known from two occurrences in unprotected forests subject to selective logging, timber harvesting for small-scale subsistence, and slash-and-burn agricultural practices (tavy).

The species is collected for horticultural purposes.

Fifteen collections representing nine occurrences have been made in seven protected areas, the Manongarivo Special Reserve (one occurrence), the Nosy Mangabe National Park (one occurrence), the Analamazaotra National Park (three occurrences), the Mantadia national park (one occurrence), the Vohibe forest-Ankeniheny-Zahamena Corridor (one occurrence), Torotorofotsy Protected Area (one occurrence), and the Tsitongambarika Natural Resources Reserve (one occurrence). Grammangis ellisii is also known from one collection (one occurrence) made in the conservation zone surrounding the footprint of a mining project and this forest should be subject to protection in the near future. The species is included in Appendix II of CITES. It is recorded in 13 ex situ collections (BGCI 2021). Individuals from this species have been brought to cultivation in the Ambatovy and Ambalabe shade house. Ex situ conservation is recommended (micro-propagation, seed banking). Further awareness building is recommended for local communities and national authorities.