This study reports effect of chemical pretreatment on pyrolysis of Arundo donax in terms of yield and composition of products. Compositional variations and structural changes in the biomass due to pretreatment were analyzed with standard techniques. H2SO4 treatment improved thermal stability with ~16% reduction in equilibrium moisture content and 1.9% reduction in calorific value, with marginal improvement with respect to grading of biomass. Alkali (NaOH) treatment effectively removed up to 87.3% lignin. Pyrolysis of native and H2SO4 treated biomass was performed in a fixed-bed semi-batch reactor. Bio-oil and char yields of untreated biomass were 31.35% and 25.68% (w/w), respectively. Pretreated biomass resulted in an improved bio-oil (34.51% w/w) and char (20.4% w/w) yield. A significant rise in carbohydrate-based furan content with a decrease in lignin-derived phenolic content was observed. The drop in carboxylic acid and aromatic oxygenate yield by 70.7% and 26.4%, respectively, improved the quality of bio-oil.