Greener composites, as alternatives to more common materials, should also achieve technical and economic feasibility to be commercially competitive. This study presents the results obtained from using a biodegradable starch-based matrix, and a natural fiber reinforcement coming from sugarcane bagasse, currently an agro-waste. The sugarcane bagasse biomass was treated to obtain four kinds of fibers with different morphological and chemical properties. The fibers were used to obtain composite materials, which were then tested for tensile properties. The results showed that some of the composites were suitable to replace high density polyethylene, from a technical and environmental point of view. The comparatively higher cost of the biobased matrices hinders the substitution, but the higher the fiber content, the lower the economic disadvantage. A micromechanical test and a sensitivity analysis showed that the fiber orientation had the highest impact on the tensile strength, followed by the fibers mean length and the quality of the interphase between the fibers and the matrix.