A field experiment was conducted during winter seasons of 1997–98 and 1998–99 with a newly released mungbean variety “Barimung-3” under varying seed rates for evaluation of yield performance in relation to growth parameters and dry matter partitioning. The treatments consisted of six levels of seed rates viz., 20, 25, 30, 35, 40 and 45 kg/ha. Among the six seed rates, 35 kg/ha gave the highest average seed yields (1382.00 and 1323.67 kg/ha, respectively). The lowest seed yields (916.67 and 839.00 kg/ha, respectively) were recorded at 20 kg/ha. All the seed rates showed the maximum leaf area index (LAI) at 63 DAE. The highest leaf area index (av. 3.72) was observed at 45 kg/ha seed rate followed by 40 kg/ha (3.59) and the lowest at 20 kg/ha (2.85). All the seed rates also showed maximum crop growth rate, relative growth rate and net assimilation rate at 63, 14 and 35 DAE, respectively. During 1997–98 and 1998–99, the highest crop growth rate (13.304 g/m2/day) was obtained at 45 kg/ha, relative growth rate (0.199 gig/day) at 35 kg/ha and net assimilation rate (4.794 g/m2/day) at 45 kg/ha seed rate.