Determination of the optimal embryo temperature for growth, maturation, nutrient utilization, hatchability, and hatchling quality has received much research attention. While several studies in other avian species have been reported, studies fine-tuning turkey hatchability have not been done. Therefore, a study looking at 4 different eggshell temperatures (99.2-99.4, 99.4-99.6, 99.8-100.2, and 100.5-101.0°F) from d 1 to 25 of incubation was conducted. Results show a decrease in hatch of fertile eggs for eggs incubated at eggshell temperatures greater than 100.5°F. Body weight and yolk free body mass were also decreased for eggs incubated at these same higher eggshell temperatures. The optimal eggshell temperature (EST) throughout incubation for turkey embryos seems to be lower than the optimum EST found for broiler embryos and this might be related to the greater turkey egg mass.