For cost effective production of endo xylanase, an enzyme of immense industrial importance, a fungal strain was isolated and identified as Penicillium janthinellum. The strain was found to ferment a number of agricultural residues in the solid state fermentation media, of which dried grass and rice straw showed promising results. The best concentration of these substrates was found to be 0.5% (w/v) and 1% (w/v) respectively at a moisture content of only 5-6%. The kinetics of endoxylanase production showed that highest enzyme production could be achieved within 72nd hours of cultivation at pH 6.0 and at 27°C. Amongst the nitrogen sources, peptone was found to be the best organic source for boosting up of the endo xylanase production. Among the metal ions tested, Mn2+ brought about a 1.15 fold increase in enzyme production in both dried grass and rice straw supplemented culture medium probably acting as a cofactor of the enzyme