Objective: To evaluate the effect of a first aid educational intervention on the aptitude, knowledge, and practices of professionals in early childhood education. Method: Quasi-experimental study of the pre and post-test type carried out in the brazilian municipality of Três Lagoas, MS. It was developed in three stages: 1) application of an online instrument to assess aptitude, knowledge, and practices about situations that require first aid; 2) educational intervention, with four theoretical meetings online and a face-to-face meeting with practical training; 3) reapplying the questionnaire. Data were analyzed using the McNemar and Bowker tests with a significance level of 5%. Results: 112 professionals participated. After the educational intervention, there was an increase in the number of correct answers for all questions related to the professionals' feeling of aptitude for all urgent and emergency situations evaluated (p≤0.05); knowledge regarding concepts related to first aid (p≤0.05); and practices in situations requiring first aid (p≤0.05). Conclusion: The educational intervention provided a significant improvement in the aptitude, knowledge, and practices of the participants. In this way, the relevance of educational actions on this theme is verified, emphasizing the importance of intersectoriality, in which health and education professionals articulate strategies to optimize first aid training actions.