Context. Each year, between 50 000 and 120 000 Asian water monitors (Varanus salvator, to >2 m total length) are harvested from the wild in Peninsular Malaysia for their skins. Under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), international trade is allowable only if it is sustainable.

Aims. To assess the sustainability of Malaysia’s harvest of water monitors by quantifying the abundance and demography of V. salvator in the wild, and to develop cost-effective methods for estimating the parameters needed to evaluate sustainability.

Methods. We conducted trapping surveys to determine the abundance, population demography and density of V. salvator in four habitat types in five states in Peninsular Malaysia in 2010, 2011, 2012 and 2018.

Key results. Of 1025 lizards captured, only 63% (mostly females) were within the preferred body-size range exploited for commercial trade. Densities were high (37–372 lizards km^–2 based on estimated population sizes; 1–35 lizards km^–2 based on number of animals captured). Anthropogenic habitats (e.g. oil palm plantations) contained denser populations of monitors than did natural habitats where no hunting occurs, but mean body sizes were smaller.

Conclusions. Despite intensive harvesting for many decades, V. salvator remains abundant and widespread. Harvesting alters the demographic structure of lizard populations, but harvests of V. salvator in Malaysia are likely to be sustainable because a significant proportion of the population is not exploited.

Implications. Ongoing monitoring is required to continually reassess harvest sustainability. For this purpose, relatively simple population approaches, such as line-trapping transects to elucidate relative abundances, can provide important data on the makeup of hunted populations of water monitors more cost-effectively than can mark–recapture studies for assessments of sustainable use of these economically important lizards.