This study evaluated 98 recombinant inbred lines (RILs) of rice, derived from the cross between Rajendra Bhagwati and Pusa Sugandh-5, to assess genetic variability, heritability and trait associations for grain yield improvement. The study was conducted at the Students' Instructional Farm (SIF) of Acharya Narendra Deva University of Agriculture and Technology in a humid subtropical climate. The research focused on 16 agronomic and physiological traits under climate conditions ranging between 30−36 °C with annual rainfall of 850−950 mm. Significant variability was observed across all traits, with high heritability estimates recorded for flag leaf area (FLA), days to 50 % flowering (DFF) and plant height (PH) at 98.77 %, 72.44 % and 67.35 % respectively. Analysis of variance (ANOVA) revealed highly significant differences for DFF, days to 100 % flowering (DHF) and biological yield, indicating strong genetic influence. High genetic advance was observed for traits such as the number of spikelets per panicle and grains per panicle, suggesting effective selection potential in breeding programs. Correlation analysis showed strong positive associations between grain yield per plant (GYP) and biological yield (BY) (r = 0.97), number of tillers (NOT) (r = 0.60) and PH (r = 0.48). Among the genotypes, the highest GYP was recorded in quantitative resistance response (QRR) rice lines QRR 251 (37.10 g), followed by QRR 426 (35.66 g), both exceeding the parental varieties. Multivariate analysis grouped the genotypes into four distinct clusters, indicating substantial genetic diversity, which holds promise for future hybridisation efforts aimed at enhancing rice productivity and resilience.