Under rainfed timely- sown condition an experiment was conducted predominantly cultivated crop Brassica species in Indian mustard (Brassica juncea L.Czern & Coss) for Principal Component Analysis and K- mean cluster analysis studies, in Randomized Complete Block Design accommodating 50 genotypes, from various Rapeseed & Mustard centres located across country, randomly in three replications during rabi 2015-16 at Tirhut College of Agriculture, Dholi, Muzaffarpur research farm. In present investigation, only first principal component (PCA1) showed maximum Eigen value and cumulatively showed 84.22% variability. Based on PCA1, PCA2 and PCA3 scores cumulatively accommodating 94.95% variability, 3-D plotted for 50 Indian mustard genotypes, covering most important traits namely AS, AB, DFF, HFS, SS-1, RV, HFPB and RL which contributed maximum towards variability. Amongst the constituted eight clusters, the cluster VIII included four genotypes, Pusa Mahak, Varuna, Pusa Bold and Rajendra suphlam followed by cluster VII with nine genotypes, reflected superiority for oil content and close for various morpho-physiological traits to cluster VIII. Most diverse genetic background was reflected by Cluster VIII (Rajendra Suplam, Varuna, Pusa Bold & Pusa Mahak); followed by Cluster III (TM-2, Divya and RH0406); Cluster V (Kanti); Cluster IV (Kranti) and Cluster VII (RH0819). Divergent cross combinations suggested namely Rajendra Suflam × Divya, Rajendra Suflam × Kanti,Pusa Mahak × Divya, Pusa Mahak × Kanti, Kranti × Divya, Kranti × Kanti, Pusa Bold × Divya, Pusa Bold × Kanti,Varuna × Divya, Varuna × Kanti, Rajendra Suflam × TM-2, Rajendra Suflam × RGN 13, Rajendra Suflam × RH 0406,RH0819× Divya and RH0819× Kanti involved cluster VIII × III,VIII × V,VII×III and VII × V involving divergent genotypes could through recombinants and utilized in hetrotic breeding. Moreover, due to superiority for most of the yield attributing traits such combinations including root parameters also could be utilized for Brassica genetic enhancement under rainfed conditions of Bihar.