The purpose of this paper is to compare trends in the bioeconomics of tropical spiny lobster and mud crab mariculture in Vietnam between 2010 and 2013 using survey processes and bioeconomic analysis. Results show that tropical spiny lobster and mud crab grow-out mariculture remained strongly economically viable in Vietnam despite significant changes in the bioeconomic environment over a three-year period. The most notable changes to the grow-out of tropical spiny lobster were a significant decrease in harvest biomass due to decreased stocking densities and poor feeding techniques. Findings highlight the potential for improvement in stocking and feeding regimes in Vietnam’s lobster and crab mariculture industry, which is likely to have positive environmental and economic benefits. There remains significant scope for increasing the size and quality of the seed used and, in the case of crabs, improvements in availability and affordability of hatchery-produced seed. Similarly, there remains significant scope for optimization of feeding rates and improvement of feeding quality.