The effect of environmentally friendly treatment using citric acid and boron compounds on the physical-chemical and mechanical properties and thermal degradation of D. asper bamboo was investigated. The chemical modification using citric acid reduced the moisture uptake of bamboo by 32%, the water absorption by 26%, and thickness and width swelling by 43% and 31%, respectively, in comparison with the reference. FTIR analysis revealed the effect of the esterification process with an increase of the carbonyl/hydroxyl absorbance ratio, which explains the reductions in water absorption and swelling. No significant change was identified on the cellulose crystallinity determined by XRD, with only a small increase of the boron-treated samples. TG/DSC measurements showed that boron compounds cause a reduction of weight loss and decrease the exothermic heat flow upon heating under synthetic air flow. However, the modification with citric acid caused slightly higher thermal degradation in the same conditions of testing, which was overcome by the addition of boron compounds in the treatment solution. Enhanced mechanical performance was observed on bamboo samples treated only with boron compounds, while samples chemically modified by citric acid presented no changes or a small increase in compression and bending properties. Nevertheless, fibre detachment and structural changes on hemicellulose/cellulose caused a small decrease in shear strength and a considerable decrease, about 30%, in tensile strength. The overall results provided an insightful understanding regarding the chemical modification of bamboo, revealing new possibilities of treatment for the improvements of dimensional and thermal stability without the use of hazardous chemicals.