A 45-day feeding trial was conducted to assess the effects of Artemia (Artemia franciscana Vinh Chau) biomass and gut weed (Ulva intestinalis) meal as replacement protein sources for fishmeal (FM) and soybean (SB) protein on the performance of black tiger shrimp (Penaeus monodon) postlarvae. The control diet had no Artemia biomass and gut weed meal, and the experimental diets were formulated to replace 20%, 40%, 60%, and 80% of FM protein with Artemia biomass meal combined with replacing 15%, 30%, 45%, and 60% of SB protein with gut weed meal. All experimental diets were formulated to be equivalent in crude protein (40%) and lipid (7%), and each dietary treatment had three replicates. Results showed that the survival of the shrimp was not significantly (p>0.05) affected by the feeding treatments. Interestingly, growth rates in term of weight, feed efficiency, and stress resistance to formalin shock of shrimp fed the diets containing Artemia biomass and gut weed meal were superior to those fed the control diet. These findings demonstrated that Artemia biomass could replace up to 80% FM protein in combination with gut weed meal replacement of up to 60% SB protein in the P. monodon postlarvae diet, with the shrimp performing best when fed a 40% Artemia biomass and 30% gut weed protein replacement diet.