In this study, a combination of three chemicals (cashew nut shell liquid, sulfited wattle tannin and copper(II) chloride) has been used to develop an environmentally friendly termite preservative. Cashew nut shell liquid (CNSL) is a by-product of cashew nut kernel processing factories and its use in the preservative formulations minimises the wastes from the factory as well as the amount of conventional hazardous preservatives from entering the environment. The formulated preservatives were tested for their ability to preserve wood blocks from a soft wood, ponderosa pine (Pinus ponderosa) and a hard wood, trembling aspen (Populus tremuloide). Sulfonated wattle tannins alone or combined with copper chloride at different concentrations, and cashew nut shell liquid (CNSL) without or with copper chloride were used in treating the 14 × 14 × 14 mm wooden blocks from the two wood species. The samples were exposed to termite attack in the surveyed fields in Arusha and Moshi, Tanzania. After 108 days exposure, evaluation of termite attack by measuring the weight losses and damage showed that the test wood treated with the combinations 40% CNSL + 1% CuCl₂ and 40% CNSL + 2% CuCl₂ were among least damaged.