The study aimed to evaluate the effect of heat stress on the developments of cacao somatic embryos under in vitro condition. Somatic embryos were induced from petal explants of ICCRI 4 cacao clone using DKW medium with the addition of 2.4-D and kinetin. Mature stage of cotyledonary somatic embryos were cultured on a germination medium and incubated at temperatures of 25 (control), 35, 40, 45 and 35 followed by 45 °C with sub-cultured on the same medium monthly. The results showed cacao somatic embryos were turned brown and suffered death after 16, 5 and 3 days of incubation at temperatures of 40, 35-45 and 45°C, respectively, while somatic embryos cultured at temperatures of 25 and 35°C could develop to form normal plantlets. The temperature of 40-45°C might be the lethal temperature for cacao somatic embryos. The results of this study gave illustration how heat stress affected cacao embryo development and could be used as a base information for developing an in vitro selection method for heat stress tolerance in cacao.