The research was conducted in a plastic greenhouse at the College of Agricultural Engineering Sciences, University of Baghdad - Jadiriyah Campus, during the 2021-2022 season, to study the effect of phosphorus, silicon, and citric acid on pepper plants using a factorial experiment design with three replicates. The first factor had three levels of phosphorus (P₂O₅): 0 kg hectare^-1 (P1), 160 (P2) and 320 kg h^-1 (P3),the second factor had three levels of potassium silicate 0 kg h^-1 (S1), 75 (S2) and 100 kg h^-1(S3), and the third factor had four levels of citric acid 0 kg h^-1 (C1), 2 (C2), 4 (C3) and 6 kg h^-1 (C4). The results of the statistical analysis showed the superiority of the P3S2C4 treatment in increasing plant height (160.20 cm plant^-1), the P2S3C3 treatment in leaf area (631.3 dm² plant^-1), the P2S3C4 treatment in the concentration of phosphorus in the leaf (0.470%), and the treatment P2S2C1 in the concentration of silicon in the leaf (18.50 ppm). The P3S3C4 treatment is the number of lateral roots (14.27 roots plant^-1). The P2S3C4 treatment is the number of fruits (48.34 fruits plant^-1) and the P3S3C4 treatment is the plant yield (3.48 kg plant^-1).