The occurrence of Fusarium species on maize, wheat and soybean in store in Southwestern Nigeria was determined followed by the study of the Zearalenone producing capacity of the isolates on soybean using wheat as standard under tested conditions. One hundred and seventy-three isolates representing 12 Fusarium species were isolated and identified as F. acuminatum, F. compactum, F. culmorum, F. equiseti, F. graminearum, F. lateritium, F. poae, F. proliferatum, F. semitectum, F. sporotrichioides, F. subglutinans and F. verticillioides. F. sporotrichioides recorded the highest isolation frequency (96%) on maize, F. graminearum (100%) on wheat and F. semitectum (80%) on soybeans. Zearalenone determination using the Veratox® ELISA quantitative test kit showed that F. equiseti (Corda) Sacc. IMI 393764 (Sos1) produced the highest zearalenone on soybean (27.2µg kg-1) under the tested conditions while no zearalenone was detected for F. poae (Sak1) and F. subglutinans (Sek2). All tested isolates produced ZEA on wheat from day 12. Kinetic study of zearalenone production showed that this toxin was not detected at day 6. The levels of zearalenone produced between day 12 and 18 at 30oC tripled on an average while at 25oC and between the 24th and 30th days, levels almost doubled. This is the first report of F. lateritium occurrence on wheat in Nigeria and zearalenone production by F. equiseti (Corda) Sacc. IMI 393764 on soybean.