This study investigated the influence of organic amendments [vermicompost (5% w/w), and hairy vetch and poultry manure biochars (2% w/w) at two temperatures (450 and 700℃)] andred soil (RS-2% w/w) on the availability of arsenic (As) to radish plants ( Raphanus sativus), earthworms ( Eisenia fetida) and microorganisms in a highly contaminated As (1341.54 mg As kg.1) soil. The bioavailability of As to earthworms was determined by mortality test and to microorganisms by microbial biomass carbon (MBC) experiment. In the plant growth experiment, there was no significant difference in dry matter content among the biochars, vermicompost and red soil and also between biochars at different temperatures. Although the extractable As increased in all the treatments after the completion of the experiment, biochars, significantly reduced the uptake of As compared to the control. Poultry manure biochar decreased As at a higher rate when compared to hairy vetch biochar, and the reduction percentage was significantly higher at higher temperature. Red soil and vermicompost also reduced the availability of As to radish but the percentage of reduction was similar to hairy vetch biochar at 450℃. Also, red soil in combination with biochars reduced the availability of As but the percentage of reduction was similar to biochars at 450℃. At the end of the mortality experiment, weight loss of worms was observed in all the treatments. The mortality percentage in worms reduced by 70-80% in biochars and RS compared to control and vermicompost treatments. The HVBC 450 and PMBC 700 markedly reduced As accumulation in worm tissues compared to control, red soil and vermicompost treatments. Microbial activity varied between the treatments and higher MBC was noticed in soils treated with biochars at low temperatures. This study shows the effectiveness of biochar and red soil in the remediation of As.contaminated soils. Results may vary, depending on the types of biochar and its pyrolysis temperature. A field experiment is currently underway to confirm the results obtained from the glass house and laboratory studies.