The aim was to investigate the efficacy of behavioural interventions as treatment of dental anxiety/phobia in adults, by conducting a systematic review of randomized controlled trials (RCTs). The inclusion criteria were defined according to the Patients, Interventions, Controls, Outcome (PICO) methodology. The study samples had documented dental anxiety, measured using validated scales [the Dental Anxiety Scale (DAS) or the Dental Fear Survey (DFS)], or fulfilled the psychiatric criteria for dental phobia. Behavioural interventions included were based on cognitive behavioural therapy (CBT)/behavioural therapy (BT), and control conditions were defined as information, sedation, general anaesthesia, and placebo/no treatment. The outcome variables were level of dental anxiety, acceptance of conventional dental treatment, dental treatability ratings, quality of life and oral health-related quality of life, and complications. This systematic review identified 10 RCT publications. Cognitive behavioural therapy/behavioural therapy resulted in a significant reduction in dental anxiety, as measured using the DAS (mean difference = −2.7), but the results were based on low quality of evidence. There was also some support that CBT/BT improves the patients' acceptance of dental treatment more than general anaesthesia does (low quality of evidence). Thus, there is evidence that behavioural interventions can help adults with dental anxiety/phobia; however, it is clear that more well-designed studies on the subject are needed.