Grafting of polyacrylonitrile (PAN) on (dewaxed and bleached) jute fibres was done by aqueous polymerization of acrylonitrile (AN) in the presence of the fiber samples employing a sodium periodate (IO4−) and copper sulfate (Cu2+) combination as the initiator. Effect of PAN grafting to different extents on X‐ray crystallinity, tensile properties, thermal behavior, whiteness index, dyeability, light‐fastness rating, and moisture regain properties of the fiber samples were studied and analyzed. Their rot resistance, determined by a standard soil burial test, were also examined and compared. Twenty to thirty percent PAN‐grafting was found to impart a most desirable balance of physical properties including fiber strength and modulus, moisture regain, whiteness index, and light‐fastness rating. PAN grafting also makes the otherwise nonresistant jute fiber significantly rot‐resistant. Morphology of the different fiber samples as studied and compared using scanning electron microscopy indicates that PAN grafting occurs on surfaces and intercellular regions as well as within the lumens of the multicellular jute fibers. © 1994 John Wiley & Sons, Inc. Copyright © 1994 John Wiley & Sons, Inc.