Justicia gendarussa Burm.f., known as gendarussa, has been used as a traditional medicine to treat thrush, headaches, bronchitis, arthritis, jaundice, otalgia, indigestion, fever, cancer, male contraception, and UV protection. J. gendarussa can grow wild as a shrub, especially in forest areas and river embankments, which can make the production of secondary metabolites inconsistent, especially phenolics group, and change the biological activity. Therefore, the purpose of this study is to determine the optimal combination of shade and nitrogen fertilizer dose for maximizing phenolic, flavonoid, and antioxidant productivity in the aerial parts of J. gendarussa. This study employed a split-plot design, with shade (0, 25, and 50%) serving as the main plot and nitrogen fertilizer doses (0, 90, 180, and 270 kg ha-1) serving as subplots. The highest productivities of phenolics, flavonoids, antioxidants, and dry weight were observed in the treatment with a nitrogen fertilizer dose of 270 kg ha-1 and no shading treatment. The dry weight of the plant's harvested aerial parts was 10.9 g plant-1. The productivity of phenolics was 210 mg GAE plant-1, while the productivity of flavonoids was 112 mg QE plant-1. Using DPPH, ABTS, FRAP, and CUPRAC methods, antioxidant productivity was determined to be 63.5; 334; 171; and 525 mol TE plant-1, respectively. Pearson correlation indicates that phenolic and flavonoid productivity is highly correlated with antioxidant productivity. Considering the research parameters of shading and nitrogen fertilizer dosage, 270 kg ha-1 nitrogen fertilizer application without shading was the optimum cultivation practice combination.