Plantain (Musa paradisiaca) is a widely cultivated plant in Nigeria which generates lots of residues (such as its peels) during its consumption. This study investigated the tensile, microstructural and moisture absorption properties of plantain peel reinforced polystyrene composites. The filler composition was varied between 0 wt% and 40 wt% and all analyses were done as per ASTM standards. The force at break and Young's modulus increased with increasing filler content and had maximum values of 405 N and 380 MPa respectively. The elongation at break point of plantain peel powder reinforced bio-composite reduced with increase in filler content, indicating that the biomass fillers led to a reduction in the deformability of the composites due to a poor transfer of stress at the weak fiber-plastic interphase. It was furthermore observed that composites with higher filler content were more susceptible to moisture diffusivity due to the hydrophilic nature of the filler powder. Microstructural analysis revealed that a more uniform distribution of the plantain fiber occurs at 40% fiber content compared to those of higher filler content.