BACKGROUND Dental fear and anxiety (DFA) refers to the fear of and anxiety towards going to the dentist. It exists in a considerable proportion of children and adolescents and is a major dilemma in paediatric dental practice. However, temperament has been suggested to be a predictive factor for the child’s reaction to dental treatment especially in young ages. This study was done to assess the role of temperament in the levels of anxiety and cooperation in preschool and elementary school children in the dental office. METHODS This descriptive, cross-sectional study evaluated 70 preschools (4 - 6 years of age) and elementary school (7 - 10 years of age) children presenting to the paediatric dental clinic of TUMS School of Dentistry. The children were generally healthy and had at least one carious primary molar requiring pulp therapy or restorative treatment under local anaesthesia. The temperament trait of children was determined using the Persian version of Malhotra’s Temperament Schedule that measures the nine temperament traits identified by Thomas and Chess. Next, the cooperation and level of anxiety in children were determined during anaesthetic injection and cavity preparation using the Venham Clinical Cooperation Scale (VCCS) and Venham Clinical Anxiety Scale (VCAS). Data was analyzed using a regression model. RESULTS The temperament trait of children had a significant correlation with their parent’s education level (P = 0.038). Lower sociability scores were significantly correlated with higher level of anxiety and uncooperative behaviour of children during anaesthetic injection and cavity preparation (P < 0.05). Rhythmicity was significantly correlated with anxiety during anaesthetic injection, and higher intensity of response/energy was significantly correlated with poor cooperation of children during injection and higher anxiety during cavity preparation (P < 0.05). CONCLUSIONS Within the limitations of this study, the results of temperament trait can predict the behaviour of children and their level of anxiety and cooperation in the dental office setting. KEY WORDS Anxiety; Cooperation; Child, Preschool; Temperament; Paediatric Dentistry.