Background: Unwanted intrusive thoughts of intentionally harming one's infant (intrusive harm thoughts) are common distressing experiences among postpartum mothers and fathers. Aim: To understand infant crying as a stimulus for intrusive harm thoughts and associated emotional responses in prepartum and postpartum mothers and fathers in response to infant cry. Method: Following completion of self-report measures of negative mood and anger, prepartum (n = 48) and postpartum (n = 44) samples of mother and father pairs completed 10 minutes of listening to audio-recorded infant crying. Post-test questionnaires assessed harm thoughts, negative emotions, urges to comfort and flee, and thoughts of shaking as a soothing or coping strategy. Results: One quarter of prepartum and 44% of postpartum parents reported intrusive infant-related harm thoughts following crying. Mothers and fathers did not differ in the likelihood of reporting harm thoughts, nor in the number of thoughts reported. Women reported more internalizing emotions compared with men. Hostile emotions were stronger among postpartum parents, and parents reporting harm thoughts. All parents reported strong urges to comfort the infant. Urges to flee were stronger among parents who reported harm thoughts. The likelihood of using infant shaking as a soothing or coping strategy was minimally endorsed, albeit more strongly by fathers and parents who also reported harm thoughts. Conclusions: In response to crying, harm thoughts are common and are associated with hostile emotions, urges to flee, and increased thoughts of using infant shaking. Reassuringly, the number of participants considering infant shaking as a strategy for soothing or for coping with a crying infant was low.