Ultisols and Oxisols are acidic soils with high concentrations of Al (Aluminium) and Fe (Iron), making them unsuitable for agriculture without intervention, which contributes to Brunei’s low agricultural self-sufficiency. Sustainable agro-waste management can enhance soil quality and crop productivity. With the increasing number of poultry farms, better management of chicken dung produced is crucial for maintaining soil fertility and enhancing maize production. This study aimed to improve selected soil chemical properties, maize yield, and above-ground biomass of maize plants by repurposing chicken dung as an organic amendment (OA). A field trial was conducted using a Random Complete Block Design with five treatments: (T1) chemical fertiliser only; (T2) 100% OA + chemical fertiliser; (T3) 75% OA + chemical fertiliser (T3); (T4) 50% OA + chemical fertiliser; and (T5) 25% OA + chemical fertiliser. Maize yield (test crop), maize plants’ above-ground biomass, and soil samples were collected and analysed using standard procedures. Results suggest that the OA treatments enhanced maize fresh cob yield and maize plants’ above-ground biomass compared with chemical fertiliser alone by 89.42% and 50.95%. Moreover, the OA increased soil exchangeable Al3+ and H+, whereas soil nitrate, P, and Na+ decreased. However, no significant differences were observed in soil pH, total organic carbon, total N, K, NH4+, Mg, and Ca2+. Further field trials may reveal the long-term soil, maize fresh cob yield, and above-ground maize plants’ biomass improvements. This study provides a novel approach to restoring Brunei's degraded agricultural soil by integrating organic amendments and promoting sustainable waste management.