This species occurs in the middle and lower storeys of primary and logged evergreen forests in lowlands and hills. It is mainly found below 600 m, although there are records up to 1,200 m (Eaton et al. 2021). It has also been recorded from peatswamp forest, luxuriant secondary forest and even cocoa plantations (in areas with adjacent forest cover).

Harpactes diardii occurs in the Sundaic lowlands, from peninsular Thailand, Sabah, Sarawak and Peninsular Malaysia, Kalimantan and Sumatra, Indonesia and Brunei (BirdLife International 2001). It formerly occurred in Singapore but is now considered extinct there, with no record since 1921.

Conservation Actions Underway
This species occurs in numerous protected areas across its range, which safeguard it from more precipitous rates of population decline. No specific measure is known.

Conservation Actions Proposed
Continue to monitor rates of population decline using habitat extent as a proxy. Protect more areas of lowland forest. Instigate longer-term monitoring at some sites to determine whether there are additional threats to habitat loss.