The present study involves a comprehensive study on the mechanical and free vibration properties of jute and carbon fibers reinforced polyester composite laminates, concentrating on the effect of addition of secondary reinforcement material (fish scale powder [FSP]). The composite laminates were prepared by using compression molding technique by varying the content of FSP (0, 1, 3, 5, and 7 wt%). The outcomes highlight the complex interaction between composite design and their characteristics. Particularly, the addition of FSP to the polyester matrix caused decrease in tensile properties due to nonuniformity in filler dispersion. Conversely, the results obtained from flexural, impact, and free vibration tests exhibited a positive correlation with the addition of FSP content. This can be attributed to the enhanced stiffness of the composites, owing to the constrained chain mobility and intricate intermolecular interactions. The hardness test results highlighted the importance of adding FSP in increasing hardness values. Scanning electron microscopic (SEM) analysis was also performed to explore the fractured morphology of the hybrid composite samples. Based on the outcomes, it is recommended to use the FSP as secondary reinforcements for fabricating composites for lightweight structural components.