Alternaria blight is one of the major biotic stresses causing heavy yield losses to the mustard crop, globally. An experiment was conducted to evaluate some rapeseed-mustard genotypes for Alternaria blight under field conditions during Rabi 2022-23 and 2023-24. The observation on disease severity, infection rate and area under disease progress curve (AUDPC) were recorded periodically and calculated as per standard procedure. Detailed analysis of data on all aspects like- PDI (%), infection rate (r) and AUDPC of each genotype/cultivar exhibited out of 262 genotypes/cultivars genotype/cultivar was found highly resistant, only 07 genotypes/cultivars found resistant, 90 genotypes/cultivars moderately resistant, 94 genotypes moderately susceptible, 63 susceptible and 8 genotypes highly susceptible indicating that substantial variation with genotypes towards disease reaction exists against the Alternaria brassicae New Delhi isolate. A total 97 genotypes were found resistance and moderately resistant with minimum PDI, apparent rate of infection and AUDPC. Among all the resistance genotype NB-115 was found best with PDI (3.42), apparent infection rate (0.061924) and AUDPC (68.3625). These resistance sources can be used in breeding programme to develop resistance cultivar for management of Alternaria blight.