Background: A careful, timely, and accurate examination of patients by nurses provides grounds for maintaining and improving patients' safety in hospitals. Proper examination of the health status of children and, consequently, an accurate nursing diagnosis can accelerate their recovery and can have positive effects on the family. Objectives: This study aimed to determine the relationship between knowledge-skill and the importance of physical examination of children admitted to infectious wards from the perspective of nurses working in Ilam hospitals in 2017. Methods: In this descriptive cross-sectional study, 150 nurses were selected using purposive sampling. To collect data, the demographic information questionnaire, physical examination knowledge-skill scale, and physical examination importance questionnaire were employed. Data were analyzed using the SPSS version 18. In addition, descriptive statistics (mean, standard deviation, frequency, and percentage) and inferential tests (independent and paired sample t-tests) were used. Results: The findings revealed that the acquired knowledge-skill mean score was 100.86 out of 200. The nurses exhibited higher levels of knowledge-skill with regard to controlling vital signs, assessment of respiratory effort, observation of skin color, and touching the extremities to check the body temperature. In contrast, they exhibited lower levels of knowledge-skill in terms of examination of the breast to assess lumps, examination of the spine, assessing how the patient is talking, and listening to lung sounds. Additionally, there was a significant positive correlation between knowledge-skill and the importance of pediatric physical examinations (P < 0.05). Conclusions: Considering that the mean score of nurses in terms of the knowledge-skill required for conducting pediatric physical examination was low, appropriate interventions should be planned by nursing managers to improve the status of nurses' knowledge-skill in this field, in order to ensure the use of the necessary procedures for effective nursing practice.