Purpose <p>Soils resulting from industrial activities are often perceived as severely degraded. However, they can exhibit unexpected and largely unexplored diversity in terms of soil health. This study aimed to assess soil health at two former thermal power plants based on soil characteristics (physical, chemical and biological properties) using a functional approach and a semi-quantitative rating method.</p> Method <p>At each site, areas corresponding to different previous industrial uses were identified, with the selection of twelve 100 m² plots that were homogeneous in terms of vegetation and soil and distinct from each other. Within each plot, a soil profile was dug, described, sampled and analysed for bio-physico-chemical parameters. A dedicated model was applied to score soil functions from a selection of explicit parameters.</p> Results <p>Evaluation of the twelve soil profiles highlighted a strong heterogeneity, reflecting contrasted past land uses and soil modifications. Even soils sharing similar land uses differed markedly in terms of soil morphology, physicochemical and biological properties. Functional scores ranged from 0.25/5 to 3.96/5, revealing different potentials as far as carbon storage, biodiversity reservoir, water regulation and plant support functions are concerned. Overall soil health ranged from “strongly degraded” to “good”, with no soil reaching the “very good” class.</p> Conclusion <p>A soil health assessment, based on a multi-parameters functional approach, was conducted on two former thermal power plant sites. An original scoring method was developed that revealed a wide diversity in soil health levels that was explained by: i) pedoclimatic conditions, ii) past land uses and iii) management practices. Despite human impact, some Technosols showed relatively good soil health, confirming the hypothesis that high anthropization is not straightforwardly correlated to the level of soil functions.</p>