Sea cucumber is a stenohaline and osmoconforming organism with a low level of tolerance to salinity change. Salinity of the medium is one of the physiological factors that affect the growth and survival of sea cucumber juveniles. This study was aimed at finding out the effect of different salinities on growth, survival and immunity rate of sea cucumber juveniles (Holothuria scabra) and finding the most suitable salinity level for optimal growth, survival and immunity rate of sea cucumber. This study used a laboratory experimental method and completely randomized design with 5 salinity treatments: 24, 29, 34, 39, and 44 ppt with 3 replications. This study used fifteen 30 L-fiber glass tanks. The sea cucumber juvenile were 4.4 ± 0.2 cm in total length and 5.6 ± 0.3 g in body weight. The juvenile densities were 15 individuals/tank, fed with fresh benthos from a culture once a day in the afternoon. Coelomate was taken from the sea cucumber juveniles from each tank and used to find out the immunity rate dan also the for osmolality. The data collected were analyzed using ANOVA that was followed by Tukey's test at 5% level of significance. The results showed that the salinity of the medium has a significant effect (P < 0.05) on the growth, survival rate and immunity rate of sea cucumber juveniles. The 24 - 34 ppt salinity can support survival rate up to 100%, high growth (6.47 – 7.10 g) and immunity rate (27 – 76 x 104 phagocytic cell/mL), while at the 44 ppt salinity has an effect not only on a low survival rate (55.6%), but also on a bad effect on osmolality (303 ± 3.5 mOs-mol kg-1), growth (3.12 ± 0.34 g), and immunity (209 x 104 phagocytic cell/mL).