The entire scientific community now agrees that sustainable development depends on environmentally friendly and renewable materials. Thus, all government policies are taking numerous steps to encourage research in this direction. The aim of the present work is to study the fracture mechanism of Sugarcane Bagasse (SCB) mortars as a function of the different treatments applied to the bagasse.To achieve this, two different types are applied toSCB. These were treatment in a sodium hydroxide solution and heat treatment at 200°C. Mortars reinforced with these different types of bagasse were then produced. The volume fractions of SCB used were 0%, 3% and 6%, giving M0 for reference mortar, MBr3 and MBr6 for mortars with untreated SCB reinforcement, MBt3 and MBt6 for mortars with heat-treated SCB reinforcement, MBc3 and MBc6 for mortars with sodium hydroxide-treated SCB reinforcement. Three-point bending tests at 28 days of age were carried out on specimens of dimensions 4×4×16cm3 obtained from the different formulations, to determine the flexural strengths. The fracture surfaces of the specimens were analyzed to understand the fracture mechanism as a function of the type of treatment applied to the SCB.The results of the studies show that all the formulations containing SCB have a flexural strength greater than that of the control mortar, with the highest strength found in the MBt6 mortar. Analysis of the fracture surfaces shows that mortars containing untreated and heat-treated SCB exhibit failure by ravelling. However, mortars containing SCB treated with sodium hydroxide break by fiber rupture.