Cultivating empathy is a presumed benefit of mindfulness, but this possibility has rarely been investigated experimentally. We examined whether a five-minute mindfulness exercise would cultivate empathy relative to two equally brief control exercises: relaxation and mind-wandering. We further examined whether mindfulness would be especially beneficial for people with autistic or narcissistic traits. Results showed no effect of mindfulness relative to both control conditions on mind reading, empathic responding, or prosocial behavior. Mindfulness effects were independent of autistic traits. Unexpectedly, people higher in autistic traits did show increased prosocial behavior across conditions. Intriguingly, mindfulness improved mind reading in non-narcissistic people, but reduced it in narcissistic people. These findings question whether a brief mindfulness exercise is sufficient for building empathy.