ABSTRACT Aims To assess the reliability and validity of a negative emotion scale for public health nurses conducting child abuse prevention activities. Design A four‐phase mixed method design. Methods Participants were public health nurses with experience in child abuse prevention across Japan. The initial scale was developed and refined based on previous studies, expert panel reviews, interviews with public health nurses, and a questionnaire‐based pilot study. In 2024, 549 public health nurses completed a questionnaire on scale items. Item analysis, exploratory factor analysis, confirmatory factor analysis, comparisons with a preexisting scale, the number of times negative attitudes and the types of behaviours exhibited by parents were used to narrow the scale and assess its psychometric properties. Results Item analysis and exploratory factor analysis reduced the scale to 15 items on two factors: ‘negative emotions toward aggressive and emotional attitudes’ and ‘negative emotions toward rejecting and uncooperative attitudes.’ Confirmatory factor analysis indicated a good model fit. The Cronbach's alpha was high, and the negative emotions scale score positively correlated with the pre‐existing scale, negative attitudes and parental behaviours. Conclusions The Cronbach's alpha coefficient and other factors confirmed the scale's reliability, and correlations with other scales confirmed its validity. Implications for the Profession Evaluating negative emotions provides critical insights into the quality of support and its influence on psychological well‐being. Impact By assessing negative emotions that public health nurses find difficult using this scale, the support system for them can be examined. Reporting Methods STROBE checklist for cross‐sectional studies was followed. Patient or Public Contribution Public health nurses were involved in the generation of items for the scale. Their perspective was sought in determining the items for the scale. Trial and Protocol Registration Registered in the UMIIN Clinical Trial Registry (UMIN‐CTR ID UMIN000054650).