One of the strategies to enhance spinach productivity is applying NPK fertilizer and organic manure. This research aims to ascertain the effect of NPK and organic manure on spinach's primary photosynthetic organ size. This study was conducted from February to April 2023 in Bajing Village, Kroya District, Cilacap Regency. The research employed a randomized block design comprising two factors: NPK fertilizer at three levels - N0 = 0 g/5 kg soil, N1 = 3 g/5 kg soil, N2 = 6 g/5 kg soil, and organic manure at three levels - P0 = 0 kg/5 kg soil, P1 = 0.5 kg/5 kg soil, P2 = 1 kg/5 kg soil. The resulting data was analyzed using ANOVA followed by a 5% DMRT test. Research findings indicate that applying NPK fertilizer and organic manure significantly affected the variables of leaf area, leaf area index, specific leaf area, leaf area span, and relative leaf growth rate at 14, 21, 28, and 35 days after sowing.