We investigated how audio-visual emotional expressions from humans and robots impact human altruistic behavior. Participants took part in the Dictator Game as “allocators” and allocated money to either a human (Study 1) or a robot (Study 2) acting as the “recipient.” After the first allocation, the recipient responded with emotional expressions of happiness or sadness through body gestures and voice. In the second round, participants allocated money again. The results showed that when the human recipient expressed sadness through body gestures, participants increased their allocation amount, regardless of vocal expressions. However, participants’ altruistic behavior towards robots was not influenced by the robot’s emotional expressions. Instead, they increased their allocation when they perceived the robot’s emotion as sadness, irrespective of the robot’s actual emotional display (happiness or sadness). These findings indicate that human altruistic behavior is present towards both humans and robots, but the triggers for such behavior differ.