Objective: To evaluate the effect of anxiety of parent accompanying child on child’s anxiety during treatment. Methods: The study included two groups: one group with 80 children whose parents were anxious, and the other group with 80 children with non-anxious parents, totaling 160 children. Each group was further randomized into subgroups, with and without parents accompanying their children. The children’s heart rates were measured using a portable pulse oximeter during the treatment. The child’s perception was measured using the Wong–Baker Faces Rating Scale, and another pediatric dentist rated child’s behavior using the Frankl scale based on the treatment video that was limited to the child’s appearance. Results: The highest pulse rates were observed in children accompanied by an anxious parent ( p < .001). Values on the Wong–Baker scale did not differ according to parental anxiety and parental presence ( p > .05). According to the dentist, the presence of parents negatively affected the anxiety of the child ( p = .025), while the effect of parents’ anxiety was not statistically significant ( p = .514). Conclusions: The anxiety of parent accompanying the child affects child’s anxiety. Parents with high anxiety appeared to negatively affect their children’s behavior.