Soybean is a very important crop used as a source of edible oil, protein and sustainable agricultural practices. Its production is extensively increasing in Ethiopia. Soybean diseases caused by fungi and bacteria are the most destructive constraints of soybean production in Ethiopia. However, distribution of the diseases has not been studied in this area. Therefore, the present study was conducted to identify the distribution of soybean diseases in southwestern Ethiopia. Purposive multi-stage sampling procedure was used to identify the locations from zone to peasant associations based on their potential of soybean production. Prevalence and intensity of diseases were assessed at 5–10 km intervals using random sampling on farmer fields. The results indicated that red leaf blotch, soybean rust, bacterial blight, bacterial pustule and frogeye leaf spot were soybean diseases observed in the study areas. The diseases were prevalent and significantly (p < 0.05) varied in intensity among the zones, districts and peasant associations. The highest prevalence and intensity of red leaf blotch and soybean rust diseases have been recorded from the Ilu Ababor and Jimma zones, respectively. This variation in the intensity of the diseases among the locations has been significantly associated with different biophysical factors. Altitude, previous crop, weed management, growth stage and crop density had significant influences on soybean diseases intensity across the locations. Overall, the present study proved that soybean diseases were found in different extents of intensity in the southwestern part of Ethiopia. Therefore, variability of the pathogens, evaluation of management options, association of agronomic practices and environmental conditions with the diseases should obtain attention to be studied. Besides, to withstand the destruction and yield losses due to the diseases, all management practices must coincide in integrated disease management for all soybean diseases with an emphasis on major diseases.