Abstract: Introduction Preoperative anxiety in pediatric patients negatively impacts their well-being, highlighting the need for effective non-pharmacological interventions. Objective To analyze the impact of a clown therapy intervention before a surgical procedure to decrease preoperative anxiety and postoperative pain in hospitalized pediatric patients and their families. Methods This quasi-experimental study took place from October 2023 to November 2024 and included children aged 3 to 12 who were hospitalized in the pediatric inpatient and resuscitation unit of a tertiary care hospital in northern Spain. A total of 204 children participated, divided into two groups. Results The mean age of children was 6.96 ± 2.72 years, and that of parents was 40.90 ± 5.77 years. Children in the intervention group showed significantly lower preoperative anxiety (mYPAS: 5.57 ± 1.49) compared to controls (6.18 ± 1.92; p = 0.012). Parental anxiety (STAI) was also lower in the intervention group (13.84 ± 7.02) versus the control group (15.63 ± 10.10; p = 0.142). Positive correlations were observed between children's preoperative anxiety and postoperative pain ( r = 0.40, p < 0.001), and between parental and child anxiety ( r = 0.19, p = 0.007). Thirty days post-discharge, children in the intervention group exhibited fewer maladaptive behaviors at home. Conclusion Clown therapy reduces preoperative anxiety in pediatric patients and may contribute to a more humanized, emotionally supportive hospital environment. Implications for practice Incorporating clown therapy into perioperative care may enhance emotional support, reduce anxiety, and improve the overall surgical experience, highlighting the importance of addressing emotional well-being.