AbstractRaw jute fiber was treated with o-hydroxybenzenediazonium salt (o-HBDS) in alkaline media. Raw and modified jute fiber were used to prepare composites by mixing with polypropylene (PP) plastic in different weight fractions (20, 25, 30, and 35%) of jute fiber. The mechanical properties except elongation at break of o-HBDS-treated (in alkaline medium) jute fiber-PP composite were higher than those of PP alone, raw jute fiber-PP composites, and alkali-treated jute fiber-PP composites. The elongation at break of treated jute-PP composite decreased to a large extent as compared to that of PP. The increase of tensile strength, tensile modulus, flexural strength, flexural modulus, and Charpy impact strength were found to be exceptionally high (in some cases ~200%) as compared to those of literature values.