The ability to mass-rear insects in high densities is a precondition for the edible insect industry but the space requirement has to be determined specifically for each species. Mass-rearing methods for Ruspolia differens Serville (Orthoptera: Tettigoniidae), one of the most consumed edible insect species in East Africa, are currently lacking. Though, these methods are urgently needed to enhance the food security in the region and to reduce the pressure on the wild populations. Here, we experimentally evaluated the effect of rearing density and rearing environment on the survival of R. differens nymphs. We conducted two experiments; in Experiment 1 we used small 0.15-liter rearing containers and in Experiment 2, larger 0.75-liter containers. The rearing densities ranged from 4 to 300 individuals per liter and we used three different rearing environments (‘net’, ‘spikes’, and ‘oat sprouts’). We found that the survival of R. differens nymphs is strongly density-dependent. The suitable rearing density for young R. differens nymphs should be ≤36 nymphs per liter, as in higher densities the mortality of nymphs increases rapidly over the course of time. With rearing densities ≤36 nymphs per liter, a survival rate of 60% can be expected up to 28 d after rearing. The studied environments only had a minor effect on the survival. These results create the basis for the efforts to upscale the rearing of R. differens in the future.