As induction of pediatric anesthesia can elicit anxiety in children and parents alike, this study was aimed at evaluating the effectiveness of clown intervention in decreasing maternal anxiety and stress in the preoperative phase. Before anesthesia induction, 25 children were randomly assigned to clown intervention and 25 to a control group with a routine procedure. In the waiting room and after separation from the child, maternal anxiety and stress were measured. The results showed that after separation, only in the clown group, maternal state anxiety significantly decreased and the tendency to somatization did not increase. Moreover, after clown intervention, older children’s mothers significantly reduced the level of perceived stress. As clown intervention can positively influence maternal anxiety and stress in the preoperative period, its promotion in clinical–hospital environments is recommended.