Objective: To evaluate the readability of orthodontic treatment informed consent forms (ICFs). Design: A cross-sectional observational investigation. Methods: An online search strategy was adopted to identify ICFs for orthodontic treatment. The text of each form that satisfied inclusion criteria was modified to a standardised protocol. The readability was evaluated using three validated instruments. GraphPad Software (GraphPad Software Inc., La Jolla, CA, USA) was used for statistical analyses. Results: A total of 59 ICFs were evaluated. The majority were available on the websites of orthodontists (66.1%) and general dentists (27.1%). The scores recorded from the three instruments indicated that the content of 93.2%–98.3% of ICFs was difficult to read. A strong correlation was observed between the Simple Measure of Gobbledegook (SMOG) and the Flesch Kincaid Grade level (FKGL) instruments (r = 0.9782; P < 0.0001). The mean SMOG score for all assessed forms was 11.19 (95% confidence interval [CI] 10.85−11.54). The ICFs authored by the manufacturers of orthodontic appliances provided by clinicians recorded a mean Flesch Reading (FRE) score of 40.14 (95% CI 33.91−46.37) out of a maximum 100. An analysis of the SMOG scores indicated that the content of ICFs authored by national orthodontic societies was more difficult to read than those written by all other authors ( P=0.01; 95% CI −1.6 to −0.2) Conclusion: The readability of the ICFs was too difficult for a significant number of the population. Many patients will be unable to validly consent to treatment based solely on reading of the content of the evaluated ICFs. A greater effort is required to improve the readability of ICFs to help ensure patient autonomy regarding orthodontic treatment decision-making and management.