This experiment was carried out during two consecutive seasons of 2014/2015 and 2015/2016 in the Baluza Research Station of the Desert Research Center, North Sinai Governorate, to study the effect of different rates of chemical fertilization (control without fertilization, 25, 50 and 75% of recommended rates) with different levels of humic acid (0, 2 and 4 kg/feddan) and their interaction, on the growth, seed yield, active ingredient and chemical constituents of Plantago psyllium L. plants. The treatment of chemical fertilizers gave significant effect on the plant height, number of branches per plant, the fresh and dry weights per plant, seeds yield per plant and per feddan also mucilage content and percentage per plant and per feddan. The treatment of 75% from the recommended dose gave the beast result. Treatment as well as humic acid gave significant effect for data recorded and the best treatment was obtained by adding humic acid at a level of 4 kg/feddan. The obtained results indicated that the interaction between chemical fertilizers at 75% from the recommended dose combined with addition of humic acid at 4 kg/feddan gave a significant effect for all data recorded.