Nowadays, more and more natural or functional fibres are being investigated due to theirutilization in thermal underwear. Kapok fibre is one of the natural cellulosic fibres whose sourceis kapok plant. It has hollow body and sealed tail, which exhibits desirable features required forfunctional textiles of this nature. In this study, cotton/kapok (80/20) blended yarns with twotypes ofyarn size 18.5 Tex and 14.8 Tex, respectively are knitted into plain stitches. The fabricsare undergone with an optimal preparation plan according to orthogonal design. Then, afterdyeing and softening, fabric properties including thermal and water-vapour resistances, wickingproperty, pilling behaviour, color fastness and surface morphology, are tested and scrutinized fortheir candidacy for thermal underwear. The results showed that cotton/kapok blended fabricshave good thermal resistance which is significantly higher than that of cotton/modal blendedfabrics, and have same water vapour resistance compared with cotton/modal blended fabricswhich are normally used as underwear. Cotton/modal blended knitted fabrics have better pillinggrade than cotton/kapok blended fabrics. Consequently, cotton/kapok blend fabrics illustratebetter rubbing fastness for drier than wet well as very good washing fastness. Meanwhile, thecotton/kapok blends fabrics have good wicking properties. Collectively, it was found thatcotton/kapok blended fabrics are appropriate for thermal underwear. However, the mainlimitation ofthese fabrics are their pilling properties.