Greenlip abalone (Haliotis laevigata) are commercially farmed in land-based systems in southern Australia and are fed formulated diets that typically do not contain macroalgae. In a 90-day study, the growth and nutrient utilization of juvenile greenlip abalone (1.82 g, 23.23 mm) fed diets containing Ulva sp. protein extract (UPE) were investigated. Animals were fed one of the four formulated test diets containing graded levels of UPE (0%, 5%, 10%, and 20%) or a commercial diet that served as a control for the 0% basal diet. Diets were formulated to contain 37% crude protein, 5% lipid, and 17.5 MJ/kg gross energy. The specific growth rate and shell growth rate (µm/day) of abalone fed the four experimental diets were similar. Dietary inclusions of UPE supported the growth of juvenile greenlip abalone and may be used to reduce dietary inclusions of solvent extracted soybean meal, dehulled lupins, and wheat flour. Currently, UPE is cost prohibitive for commercial use in greenlip abalone diet. As UPE is a by-product of the macroalgae industry, the cost of UPE would likely become more economically viable as macroalgae production increases in the future to include in diets for greenlip abalone. Once economically viable, we recommend a dietary inclusion of up to 20% UPE meal for greenlip abalone.