This review on Alternaria blight caused by singly or by mixed infection is one of the most widespread and destructive disease of oilseed brassicas in all the continents. These pathogens are necrotrophs. The disease appears as black spot but later on enlarge and develops into prominent round spots with concentric rings. Many spots coalesce to form large patches showing blight and cause defoliation in severe cases. The spots on the mid-ribs of the leaves are linear and sunken. Circular to linear lesions also develop on stem and pods, which elongate at later stages. Infected pods produce small, and shrivelled seeds. This disease causes substantial yield losses as a result of several factors including reduced photosynthetic potential, early defoliation, flower bud abortion, premature ripening, siliquae dehiscence, seed shrivelling and reduced seed size, impairs seed colour and reduced oil content. This paper reviews the research on the development of Alternaria blight, describes the pathogens of Alternaria blight on rapeseed-mustard, which includes geographical distribution, economic importance, symptoms, habitat and host range, pathogen taxonomy, survival, pathogenicity and disease development, epidemiology, host resistance, breeding for disease resistance, genotypic stock, and management.