This study investigated whether a clown doctor intervention could reduce preoperative anxiety in children hospitalized for minor surgery and in their parents. A randomized controlled trial was conducted with 77 children and 119 parents: the clown group consisted of 52 children accompanied in the preoperating room by their parents (n = 89) and two clowns while the comparison group consisted of children accompanied by the parents only. The clown intervention significantly reduced the children’s preoperative anxiety: children benefited from the clown’s presence and showed better adjustment than children in the comparison group. No significant results were found in parents.