Arboreal mammals are often hard to detect with traditional techniques, and this can have consequences for their conservation. For example, the true conservation status of Lumholtz’s tree-kangaroo (Dendrolagus lumholtzi) – which is found in rainforests of Queensland’s Atherton Tableland Region – is uncertain due to low detectability by standard survey techniques. We aimed to improve methods for monitoring Lumholtz’s tree kangaroo. We surveyed rainforests in north Queensland using daytime surveys, night-time spotlighting and thermal imaging to compare detection rates of animals by these methods. We also conducted a similar small-scale survey testing these methods for small mammals in a semi-arid environment. Both studies showed that thermal imagers were more efficient and effective at detecting the target animals than spotlighting.