Xylanase breaks xylan down to xylose, which is used in industries such as pulp and paper, food and feed, among others. The utilization of wastes for xylanase production is economical, hence this work aimed at producing xylanase through solid-state fermentation and characterizing the enzyme. Xylanase-producing strains ofBacillus megateriumandAspergillus nigerGIO were inoculated separately in a 5 and 10 day solid fermentation study on maize straw, rice straw, sawdust, corn cob, sugarcane bagasse, conifer litters, alkaline-pretreated maize straw (APM) and combined alkaline and biological-pretreated maize straw, respectively. The best substrate was selected for xylanase production. The crude enzyme was extracted from the fermentation medium and xylanase activity was characterized using parameters such as temperature, cations, pH and surfactants. Among different substrates, the highest xylanase activity of 3.18 U ml−1was recorded whenA. nigerGIO was grown on APM. The xylanase produced byA. nigerGIO andB. megateriumhad the highest activities (3.67 U ml−1and 3.36 U ml−1) at 40 °C after 30 and 45 min of incubation, respectively. Optimal xylanase activities (4.58 and 3.58 U ml−1) ofA. nigerGIO andB. megaterium, respectively, were observed at pH 5.0 and 6.2. All cations used enhanced xylanase activities except magnesium ion. Sodium dodecyl sulfate supported the highest xylanase activity of 6.13 and 6.90 U ml−1forA. nigerGIO andB. megaterium, respectively. High yields of xylanase were obtained fromA. nigerGIO andB. megateriumcultivated on APM. The xylanase activities were affected by pH, temperature, surfactants and cations.