In this study, carboxymethyl cellulose/halloysite nanotube (CMC/HNT) bio-nanocomposite films were prepared by solution casting method. The effects of HNT content and chemical modification using sodium dodecyl sulfate (SDS) on the mechanical, morphological and thermal properties of CMC/HNT bio-nanocomposite films were analyzed. Fourier transmission infrared proved the chemical modification of HNT using SDS was successful. Increasing in HNT content had increased the tensile strength at optimum of 10 wt%. The modulus of elasticity and elongation at break were also increased. The SDS-treated bio-nanocomposites possessed higher mechanical properties compared to untreated bio-nanocomposites. The improvement of dispersion and interfacial interaction of HNT in CMC matrix were observed by field emission scanning electron microscopy images. For untreated samples, the XRD results showed that the peak intensity correlated with crystallinity increased and also increased the basal spacing at 10 wt% of HNT in the bio-nanocomposites. The SDS-treated bio-nanocomposites further increased the peaks intensity and the basal spacing compared to untreated bio-nanocomposites. Meanwhile, the moisture content of SDS-treated bio-nanocomposites is much lower compared to the untreated bio-nanocomposites. The thermal stability of CMC/HNT bio-nanocomposites increased with increasing HNT filler content. The SDS-treated bio-nanocomposites had higher thermal stability compared to untreated bio-nanocomposites.