The polyculture of sea grape with whiteleg shrimp is considered as one of the strategic approaches to sustainable shrimp production. This is the first study to investigate the effects of integrating sea grape (Caulerpa lentillifera) with different densities of whiteleg shrimp (Litopenaeus vannamei) on water quality, shrimp performances and sea grape proximate composition. The experiment was executed in indoor tank systems, comprising five treatments in randomly designed triplicate tanks, with five levels of shrimp densities (100, 200, 300, 400, and 500 individuals m^-3) integrated with sea grape (1 kg m⁻³) for 56 days. The results showed that the polyculture of sea grape with shrimp significantly enhanced sea grape biomass and proximate composition in terms of protein, lipid and ash contents while maintaining adequate levels of total ammonia nitrogen (TAN), nitrite (NO₂⁻), nitrate (NO₃⁻), and phosphate (PO₄³⁻) in the rearing tanks at high shrimp densities. Shrimp growth rates (weight gain, daily weight gain, and specific growth rate) tended to decrease at higher density levels, but there were no statistical differences (p > 0.05) among treatments at stocking densities ranging from 200 to 400 individuals m^-3. Although shrimp survival was significantly reduced as stocking densities increased from 400 individuals m^-3 upward; the lowest and highest shrimp yields were obtained at densities of 100 and 400 individuals m^-3, respectively. Feed conversion ratios were higher at higher shrimp density; however, no significant difference was not observed between 300 and 400 individual m^-3 groups. These findings indicated that polyculture of sea grape with whiteleg shrimp can perform up to 400 individuals m^-3 while maintaining suitable water quality parameters and sustaining improved production efficiency in the culture unit.