A caffeine overdose is most likely to result from the consumption of nutritional supplements or caffeine pills. Herein, we describe two fatal cases of caffeine intoxication. Case 1: A Japanese man in his 30s was found dead, with two bottles of water and unopened tablets for motion sickness near his body. Caffeine concentrations were 99.6 μg / mL in the cardiac blood and 169.1 μg / mL in stomach contents. Case 2: A Japanese man in his 40s was found dead, with an empty bottle of caffeine and six empty boxes of Travelmin ( a motion sickness medication ) in a trash can. Caffeine concentrations were 79.6 μg / mL in the cardiac blood and 876 μg / mL in the stomach contents. Fatal caffeine poisoning is comparatively uncommon, but it has recently been increasing due to the easy availability. For the prevention of caffeine overdoses, there should be heightened public awareness of the potential dangers of a caffeine overdose.