Natural plant growth stimulants showing promising alternatives to chemical fertilizers. The efficiency of T. harzianum spores (TH) or metabolites (MT), and Humic acid (HA) were investigated as an additive and plant growth stimulant in hydroponically grown Nigella sativa plants. Plant height, Number of leaves, branch numbers, leaves area, leaves fresh and dry weight; total chlorophyll, % of NPK, carbohydrates content and % of oil content were measured at the end of the growing season. Results showed that, full Hogland solutions were significantly different in all studied parameters. Natural additives also, enhanced the efficiency of the nutrient solution and increased plant growth. T. harzianum spores significantly enhanced plant growth promotion as it increased plant biomass 45% more than the control; followed by 34.5% increase for T. harzianum metabolites, and 20.6 for Humic acid. The same trend was observed in all vegetative characters, seed characters and chemical properties of Nigella sativa oil content. Total essential oil and NPK were increased significantly in the treated plants with T. harzianum spores. Briefly, all bio-additive treatments increased plant growth, seed, and oil contents in hydroponic growth system.