The present study was conducted to investigate the effect of seaweed extract (SWE)on morphological indices and carbohydrate accumulation of two rice cultivars under aerobic conditions. The experiment was laid out in factorial completely randomized design (CRD) with three replications. SWE @ 10.0%, 12.5% and 15.0% w/v were applied as soil drench at 3 DAS. The results revealed that SWE application showed positive effect on plant vigour, biomass production and total leaf area in both rice cultivars. SWE application showed negative effect on number of leaves in cultivar PR 116. Relative growth rate and vigour index was recorded higher in cultivar PR 116 as compared to Nagina 22. The increase in total soluble sugar and starch content was also observed in both cultivars with SWE application. It was concluded that SWE had a promontory effect on the morphological attributes and carbohydrate accumulation under aerobic conditions but effect was found to be more pronounced in cultivar PR 116.