Based on former exploratory research, we used seaweed (SW) fiber as a novel biofiller for the production of polypropylene (PP) biocomposites. Maleic anhydride-grafted polypropylene (MAPP) and a CNT masterbatch (CESA) were applied as compatibilizers. Mechanical properties, crystallization behavior, dynamic mechanical performance as well as interfacial morphology were characterized. SW fiber was successfully incorporated in the PP matrix in terms of mechanical reinforcement. Accelerated crystallization process of PP matrix was observed. DMA results also indicated the favorable adhesion between SW fiber and PP matrix, which could be confirmed by SEM characterization. The effect and efficiency of MAPP and CESA as compatibilizers were evaluated. Moreover, potential flame retardancy of SW fibers for PP matrix was observed, and satisfying results warrant further investigations. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 118: 997-1005, 2010