Fly ash is a solid residual by-product of coal combustion in thermal power plants and considered a problematic solid waste. To justify the application of fly ash in agriculture, the Pha Lai (Vietnam) thermal power plantderived fly ash (FA) was amended, along with farmyard manure (FYM) and NPK chemical fertilizer (NPK), to sandy soil in Quang Binh (Vietnam) for peanut (Arachis hypogaea L.) cultivation. The effect of FA amendment was investigated, based on the changes in soil properties and peanut yields. The results revealed that the FA amendment had positive benefits to soil properties and peanut yields. Especially, the amendment of 5% FA in combination with FYM and NPK increased notably the proportion of silt-sized particles, surface charges, pH, electrical conductivity, cation exchange capacity, contents of Ca 2+ and Mg 2+ , contents of total and available P and K, and hydraulic conductivity. Microbial populations, enzyme activities, and bacterial community diversity were considerably improved. More dominant species, viz. Paraburkholderia sacchari, Rheinheimera tangshanensis, and Betaproteobacteria bacterium, were observed. Moreover, the FA increased dry peanut grain yield from 0.19 to 2.3 t/ha (12.1-fold). It is recommended to utilize 5% FA along with FYM and NPK in peanut production for economically valuable and environmentally friendly disposal.