This study was conducted to determine the effect of NPK (15 : 15 : 15) fertilizer on some growth parameters of Punica granatum seedlings towards establishing the fertilizer amount optimal for the growth of P. granatum. Planting bags containing 23.3 kg of soil were used for planting the seeds of Punica granatum, and the soil was treated with different amounts of NPK 15 : 15 : 15 fertilizer (T1 = 0 g, T2 = 1 g, T3 = 2 g, T4 = 3 g, and T5 = 4 g) and watered daily with borehole water. The experiment was laid out in a completely randomized design with four replicates. Data were taken on the number of leaves (NOL), height of plant (HOP), and area of leaves (AOL) every three weeks for fifteen (15) weeks after planting. Results obtained using the Ochekwu Comparative Treatment Average (OCTA) trend showed that all the parameters under investigation increased significantly with an increase in fertilizer amount compared to the control. The optimum growth was observed to range between T3 and T4 for the number of leaves, height of plant, and area of leaves parameters studied. It was also observed that the increment of fertilizer amounts beyond this optimum point reduced biological yield previously obtained. Hence, for the optimum growth of P. granatum seedlings, NPK (15 : 15 : 15) fertilizer should be applied within the range of T3 and T4 or any other measurement that falls within the concentration range of T3 (0.09 g NPK kg−1 soil) and T4 (0.13 g NPK kg−1 soil) in the Niger Delta of Nigeria.