We examine how betrayal aversion and ambiguity attitudes influence trust. To disentangle these effects, we use a Trust game and manipulate trustors’ perception of being the intentional recipients of trustees’ betrayal by varying the nature of the latter: a human or a machine that replicates human choices in probability. After confirming that this manipulation does not affect ambiguity attitudes or beliefs about others’ behavior, we find that both factors significantly influence trust. Nonetheless, even when controlling for these attitudes and beliefs, participants exhibit lower trust in humans than in machine. Furthermore, using Noldus' FaceReader technology to measure emotions during trustors’ decision-making process, we find that participants express greater anger toward human trustees. Our results indicate that both betrayal aversion and ambiguity attitudes play important roles in shaping trust decisions.