This study presents a combination of three different pretreatments of sugarcane bagasse (SCB) aimed at increasing levoglucosan (LGA) yield during fast pyrolysis. SCB samples were subjected, individually or in combination, to the following pretreatments: distilled-water leaching, torrefaction at 290 °C for varying residence times (5, 7.5, and 10 min), and fungal decay employing white rot (Trametes versicolor) or brown rot (Coniophora puteana) over durations, ranging from 2 to 12 weeks, respectively. The combined pretreatment of torrefaction (5 min) and fungal degradation by C. puteana for 12-weeks considerably reduced the hemicellulose (by 61.04%) and lignin (by 56.61%) content of the SCB, while increasing the cellulose concentration by 153.4%, leading to enhanced LGA production during fast pyrolysis. Additionally, the optimal pretreatment conditions involved water-leaching followed by torrefaction for 7.5 min at 290 °C, combined with and the action of the white rot fungus Trametes versicolor during 4 weeks which after rapid pyrolysis leads to the highest LGA yield of 11.59%. The combined pretreatments effectively improved SCB's chemical composition and enhanced the properties of its bio-oil produced during fast pyrolysis process.