Soils provide important ecosystem services, including climate and nutrient cycling regulation, and food supply, which can be compromised by their degradation. According to the European Commission’s Joint Research Centre (JRC), above 60 % of European soils are in an unhealthy state, which mainly consists of the loss of soil organic carbon (SOC) and biodiversity. Consequentially, is crucial to explore innovative strategies to improve soil health and productivity. However, laboratory assays can be essential for testing soil restoration strategies and excluding any adverse effects before field application. This study explored the effectiveness of hydrochar, a possible soil improver derived from thermochemical conversion of organic residues, in enhancing health of agricultural degraded soils. In a pot experiment, five soil treatments were compared: hydrochar derived from sewage sludge or from thistle (Cynara cardunculus L.) residues applied at two doses (34 and 68 g kg^-1), and a control without hydrochar. After three exposure times (18, 92, 146 days), 19 key indicators of soil health were assayed: microbial biomass (C_mic), total microbial activity (soil respiration), specific activities related to nutrient cycling (respiration responses to 11 substrates), bacterial genetic richness, pH, total organic carbon content (C_org), and its extractable and mineralizable fractions, cation exchange capacity. A weighted soil health index (SHI_w) was developed by selecting a minimum data set (MDS) of indicators using multivariate analysis. Results showed that hydrochar application did not cause adverse effects on soil microbial community, playing a crucial role in nutrient cycling, but generally improved microbial activities, soil pH and C_org.  SHI_w obtained from a MDS of five indicators (C_mic, respiration, respiration response to L-asparagine, pH, C_org) confirmed a significant improvement in soil health across all hydrochar treatments, and exposure times. Further researches are needed to confirm long-term persistence of hydrochars’ beneficial effects and to assess its applicability in field conditions.