This study was conducted to investigate the effect of wood ash solution on chemical composition of cashew nut shell. Approximately 200g, 400g, and 600g of wood ash were weighed into separate plastic containers. 1 litre of the wood ash solution containing 200g, 400g, 600g and 0g of wood ash respectively was used to soak 200g of the milled cashew nut shell for 24 hrs to make four treatment, which was replicated thrice in a complete randomized design. Result showed that milled cashew nut shell treated with 600g wood ash has lower phenolic compounds (tannin and phenol) and high level of crude protein and calcium. It can therefore be concluded that 600g/L wood ash solution would be preferred for treatment of cashew nut shell in order to neutralize to a minimal level the acidic content of the cashew nut shell and improve the nutritive value particularly in terms of crude protein, and mineral content.