1. Global targets to halt biodiversity losses and mitigate climate change will require protecting rainforest beyond current protected area networks, necessitating responsible forest stewardship from a diverse range of companies, communities and private individuals. Robust assessments of forest condition are critical for successful forest management, but many existing techniques are highly technical, time-consuming, expensive, or require specialist knowledge. 2. To make assessment of tropical forests accessible to a wide range of actors, many of whom may be limited by resources or expertise, the High Conservation Value Resource Network (HCVRN), with the SE Asia Rainforest Research Partnership (SEARRP), developed a South East Asian version of the Forest Integrity Assessment (FIA) tool as a rapid (< 1 hour) method of assessing forest condition in the field, where non-experts respond to 50 questions about characteristics of the local environment while walking a site transect. Here, we examined the effectiveness of this survey tool by conducting ~ 1,000 assessments of forest condition at 16 tropical rainforest sites with varying levels of disturbance in Sabah, Malaysian Borneo. 3. We found good agreement (R-squared range: 0.50 – 0.78) between FIA survey scores and independent measures of forest condition, including biodiversity, vegetation structure, aboveground carbon, and other key metrics of ecosystem function, indicating that the tool performed well. Although there was variation among assessor responses when surveying the same forest sites, assessors were consistent in their ranking of those sites, and prior forest knowledge had a minimal effect on the FIA scores. Revisions or further training for questions where assessors disagree, for example on the presence of fauna at a site, could improve consistency. 4. We conclude that the FIA survey tool is a robust method of assessing forest condition, providing a rapid and accessible means of forest conservation assessment. The FIA tool could be incorporated into management practices in a wide range of forest conservation schemes, from sustainability standards, to community forestry and restoration initiatives. The tool will enable more organisations and individuals to understand the conservation value of the forests they manage, and to identify areas for targeted improvements.Minhyuk Seo