Heavy metal (HM) pollution coupled with soil acidification has posed an increasingly severe threat to agricultural sustainability of tropical region in the world. However, minimal research has been conducted on the remediation of HM contaminated soils in this region. In this study, a vermicopomst (VC) produced from vermicomposting cattle manure in a tropical rubber plantation was applied to remediating a tropical acidic soil in Hainan, China. The effectiveness of VC in reducing available HM in soils was evaluated by incubation experiments with spiked Cd, Cr and Ni or Cd contaminated field soil. The dynamic changes of soil physical, chemical and biological properties after VC amendment were determined to explore the mechanisms of HM immobilization. The results showed that VC amendment significantly reduced 0.01M CaCl₂ extractable amounts of Cd, Ni and Cr in the HM-spiked soils. CaCl₂ extractable Cd was reduced by 49% when VC was amended to Cd contaminated cassava planting soil. Thermodynamic studies showed that VC had a high adsorption capacity for Cd, Ni and Cr, with the maximum adsorption (obtained from the Langmuir model) of 33.45, 26.17, and 20.88 mg/g, respectively. The reduction in CaCl₂ extractable HM after VC amendment was consistent with the order of maximum adsorption for Cd, Ni, and Cr on VC. Vermicompost amendment increased soil pH by 0.7 to 1.5 units, which is positively related with VC rate, but negatively with the decrease in extractable HM. These results indicates that adsorption of HM onto VC and an increase in soil pH after VC amendment are likely responsible for the decreased availability of Cd, Ni, and Cr in the contaminated soil. In addition, the addition of stable organic substances and subsequent formation of water-stable aggregates may be also beneficial for immobilizing HM and improving tropical soil quality.