Second-generation biomass has been proposed as an alternative way to provide sustainable energy. However, the transformation of biomass into liquid by thermoconversion introduces several drawbacks in the bio-oil. A new approach to convert biomass into a more stable and less polar biocrude compared to fast pyrolysis bio-oil was recently developed, which is based on hydrolysis/functionalization of biomass carbohydrates. This work describes the transformation of sugar cane bagasse and Jatropha curcas cake in biocrude through the acetylation reaction under microwave radiation, in the presence of acetic anhydride and a catalytic amount of sulfuric acid. The reaction conditions were broadly investigated and moderate to complete conversion of the biomasses was achieved; however, Jatropha curcas was more resistant than sugar cane to the hydrolysis/acetylation reaction. The produced biocrudes were thoroughly characterized, and polyacetylated carbohydrates were the main products identified.