The integrated aquaculture-seaweed system has been identified as a bio-mitigation strategy to overcome environmental damage, improve the efficiency of nutrient use, maintain good water quality, and ensure the system’s sustainability. This study was conducted to determine the appropriate density of sea grape (Caulerpa lentillifera) in polyculture with whiteleg shrimp (Litopenaeus vannamei) in the same culture tank. Five treatments were randomly designed in triplicate tanks where shrimp was monocultured (without sea grape) as a control treatment and four polyculture treatments with different seaweed density levels (0.5, 1, 1.5, and 2 kg m 3) for 56 days. The results showed that polyculture of shrimp and sea grape significantly reduced the concentrations of total ammonia nitrogen (TAN), nitrite (NO2  ), nitrate (NO3  ), and phosphate (PO4 3 ) in the rearing tanks and significantly improved (p < 0.05) the growth rate (6.67–6.76% day 1), survival (73.3–78.5%), and production of shrimp (3.44–3.87 kg m 3) compared to monoculture (6.24% day 1, 54.8%, and 2.02 kg m 3, respectively). Applying shrimp and sea grape polyculture at a density of 1 kg m3 provided a relatively better shrimp performance and feed conversion ratio than other seaweed densities, although not significantly different among polyculture treatments. The findings suggested that sea grape could be used at densities of 0.5–2 kg m 3 in polyculture with whiteleg shrimp, of which 1 kg m 3 resulted in higher production and feed efficiency.