Organic soil amendments offer promising potential to improve soil properties and plant growths. However, data on these benefits of compost and biochar in a tropical environment are limited. We investigated the impacts of compost (C) and coffee-husk biochar (B) sole- and co-application at various amounts (0%C:0%B, 0%C:100%B, 100%C:0%B, 25%C:75%B, 50%C:50%B, 75%C:25%B and 100%C:100%B) on soil properties and Desho grass growth on acidic soils in a tropical environment. Soil texture, pH, CEC, organic matter (OM), organic carbon (OC), total nitrogen (TN) and available phosphorus (AP) plus plant growth parameters were measured. Both sole- and co-applications of compost and biochar had positive effects on soil properties and plant growth. Compost and biochar co-application at full rates showed the highest soil property and plant growth improvements relative to control followed by co-application at half rates for TN, AP and plant growth and biochar sole-application for pH, OM, OC and CEC. However, the sole-application of compost and biochar showed the lowest increases relative to control in pH, CEC, OM and OC, and in AP and plant growth, respectively. Overall, compost and biochar could be co-applied at full rates on acidic soils in a tropical environment to improve soil property and plant growth.