Harsh parenting (HP) entails physical and verbal expressions of anger and aggression toward children, usually observed as response to child negative emotionality. Abundant previous research has indicated the detrimental negative impacts of HP on children's developing behavioral, cognitive social, and emotional capacities, highlighting the need for examining its determinants. Among other determinants, previous research has suggested the importance of parents' cognitive regulatory capacity for inhibiting inappropriate behavioral responses (response inhibition; RI). Specifically, parents' RI may help prevent the translation of harsh tendencies into HP behavior. Previous research in the field has typically focused on investigating parents' trait capacities of RI, though particular state capacities of RI in the context of children's negative emotions might be more relevant. The current study is the first to investigate whether the latter more specifically associates with HP. Data were collected in 2019. Participants were 98 first-time parents (M age = 31.85 years, SD age = 4.22), 68.0% mothers. Parents completed a computerized Go/No-Go paradigm, measuring RI in seven different background conditions: one neutral-gray background condition and six emotional face background conditions (infant negative/positive/neutral emotional faces and adult negative/positive/neutral emotional faces). Next, participants reported on their HP. Results indicated that parents' RI was significantly lower in infant emotional contexts, as compared to adult emotional contexts. Moreover, parents' RI was significantly lower in infant negative emotional contexts, compared to infant positive emotional contexts and infant neutral emotional contexts. Importantly, lower RI in infant negative emotional contexts is associated with increased HP. These results have important implications for affective science as well as practical implications for early detection and intervention of HP tendencies toward infants.