Soy protein concentrate (SPC) is a refined plant protein with fewer antinutritional components than conventional soybean meal (SBM), which may allow for increased performance or higher level of incorporation in the feed. We studied the effects of gradual SBM substitution with SPC on growth performance, feed utilization, and whole-body composition of juvenile Pacific white shrimp reared in an indoor biofloc system for 10 weeks. Six isonitrogenous and isolipidic diets (35% crude protein, 8% lipid) were formulated using 6% fishmeal. The basal diet had ~48% SBM and 0% SPC. Five test diets substituted SBM with SPC at varying percentages (5, 10, 15, 20, and 30%). Each diet was offered to four replicate 150-L tanks (80 shrimp per tank at first), in four feedings per day. At six weeks, shrimp were partially harvested, and data were recorded. Subsequently, 52 shrimp were returned to their respective tanks, and the trial was continued for another 4 weeks. At 6 weeks, no significant differences (p>0.05) were observed among diets in growth performance parameters. At 7-10 weeks, also no significant differences (p>0.05) were observed, whereas cumulative data up to 10 weeks showed a slight difference in FCR (p=0.0218) whereas growth and survival did not differ (p>0.05). Final whole-body proximate composition was not significantly different among treatments (p>0.05) except for fat. Crude fat was slightly greater in the 20% SPC group (5.55%) than in the 5-10% SPC groups (4.06-4.22; p=0.0135). Overall, the results show that partial substitution of SBM with SPC up to 20-30% results in good growth and survival of biofloc-reared L. vannamei equivalent to a high-SBM control.