Accurate knowledge of distribution and population size is required for effective conservation and management of wild species. Here we report on the first estimates of the distribution and density of the green python (Morelia viridis), an iconic rainforest species widely kept in captivity. We used climatic modelling to predict its distribution in Papua New Guinea, and both climate and vegetation mapping to predict its Australian distribution. We used mark–recapture methods to estimate the density and population structure of green pythons at Iron Range, northern Australia. Bioclimatic analyses suggested that there is extensive climatically suitable habitat in Papua New Guinea (≥200 000 km²), but very little in Australia (~300 km²). However, use of vegetation maps increases the predicted suitable area of occupancy in Australia to 3127 km², including nine regional ecosystems. Density estimates at Iron Range were 4–5 ha^–1 in the complex vine forest regional ecosystem; however, only half of these were mature adults. The large predicted area of occurrence and the high density in the one intensively studied area suggest that the species is not vulnerable to extinction in the short term. However, more studies are needed in both New Guinea and Australia, especially to quantify the impact of harvesting green pythons for the pet trade.