A photo-crosslinkable polyolefin composition comprises a polyolefin, a source of functionality receptive to crosslinking by UV radiation, a cationic photoinitiator and optionally includes a free-radical photoinitiator, a crosslinking accelerator or sensitizer, and other additives such as compatibilizers, inorganic fillers, nanofillers, glass, polymeric and ceramic microspheres, glass fibers, flame retardants, antioxidants, stabilizers, processing aids, foaming agents and pigments. A method for manufacturing a UV-crosslinked polyolefin article comprises forming an article by extruding, molding or otherwise forming the UV-crosslinkable polyolefin composition and subjecting the article to UV radiation on-line with the extrusion, molding or other forming operation.