Field experiments were carried out at the experimental Station of National Research Center Nubaria region, Behira Government, Egypt, to investigate the effect of different levels of nitrogen fertilizer, tryptophan and their interaction on the growth, productivity and some chemical constituents of green onion plant (Allium cepa L. cv. Giza 6)at 48 and 63 days after sowing (stage A and B respectively). Obtained results indicated that both nitrogen and tryptophan application significantly promoted the growth criteria of green onion: shoot length, white part length, bulb diameter, number of leaves, fresh and dry weight of onion plant at two vegetative stages. The increase in growth criteria was concomitant with increases in photosynthetic pigments, oil percentage, absorbed nitrogen, total nitrogen, total protein, total free amino acids and indoles content. Also, the results cleared decrease in the total soluble salts (TSS). It was noted that 30kgfed-1nitrogen and 50 mg/L tryptophan caused the highest increases in all examined growth parameters of onion plants at both growth stages. It means that tryptophan amino acid application reduced recommended nitrogen dose at rate 75% and consequently reduced nitrogen accumulation and cost.