Abstract: Field trials were conducted on black cumin (Nigella sativa L.), sprayed with either deionized water (control) or 10-5 M GA3 at 40 (vegetative stage) or 60 (flowering stage) Days after Sowing (DAS) to characterize the effects of hormone treatment on the mentioned parameters and select the suitable growth stage for spray in order to achieve desired results. Shoot length/plant, leaf number/plant, leaf area/plant, branch number/plant, dry weight/plant and accumulations of N, P and K were assayed at 70 DAS. Capsule number/plant, seeds capsule-1, 000 seed weight, seed yield q ha-1, harvest index and Seed Yield Merit (SYM) were analyzed at harvest (130 DAS). It was noted that growth, NPK accumulation and seed yield were maximal when spraying of GA3 was carried out at 40 DAS. However, spraying at 60 DAS was not much effective in terms of the parameters studied. Moreover, there was a significant difference in spray treatments at various growth stages only when GA3 was sprayed and not when water was sprayed.