Live-fish transportation is an essential feature of aquaculture. However, during the transportation process, factors such as fish size, packing density, and variations in water quality can impact fish survival. The fourfinger threadfin (Eleutheronema tetradactylum) is an important economic marine fish in Taiwan. To date, adequate information about optimal practices for the transportation of fourfinger threadfin is still limited. To establish the appropriate conditions for live transportation of juvenile fish, the present study investigated (1) the suitable handling size of juveniles, and (2) the survival of juveniles and the variation of water quality at different packing-densities. The results showed that the survival of juveniles of different sizes (S = 16.86 ± 1.39, M = 21.37 ± 3.07, and L = 36.50 ± 4.03 mm) was significantly higher in M and L sizes than that in S size at 24 hr after handling. We subsequently investigated the survival rate and water qualities of M size fish in 3 packing densities (1,000, 2,000, and 3,000 fish/bag; water volume per bag = 6.25 L) after 5 hr of simulated transportation. The highest survival rate (99.53 ± 0.20%) was observed with a density of 1000 fish/bag. The analysis of water quality parameters showed that pH decreased with density; in contrast, NH3-N and NO2--N increased with density, and the deterioration of water quality was significantly higher in the 3,000 fish/bag per bag than that in the other two groups. To summarize, we recommend that juveniles should be at least 20 mm in size, transported in a packing density of 1,000 fish/bag, and with transport time no longer than 5 hr.