Several insect species are mass produced for animal feeds, fish bait, or human consumption. The yellow mealworm, Tenebrio molitor L. (Coleoptera: Tenebrionidae), is one of the more-popular insects considered for this use. To make T. molitor competitive with more-traditional protein sources, mass production must be optimized. Herein, we review the scientific literature on the range and optimal environmental, physical, and dietary conditions for the rearing T. molitor. Our review identified that: (a) the optimum temperature for T. molitor growth is 25–28°C; (b) T. molitor larval growth rate is greatest at ≥70% relative humidity (RH) with an optimum range between 60–75% RH, and; (c) optimal growth is achieved with diets containing 5–10% yeast, 80–85% carbohydrate, and the addition of B-complexvitamins.