Background: Low back pain (LBP)-related misbeliefs are a risk factor for chronicity and thereby require further attention. Objective: To assess the influence of a mediatised video on LBP-related misbeliefs in the general population and to examine whether these individuals intended to change their behavior to protect their back after viewing the video. Method: French-speaking adults within the general population were recruited through advertisements and were asked to complete a self-administered questionnaire, available online between January 2021 to April 2021. The questionnaire asked about socio-demographic information and back pain beliefs (the 10-item Back-PAQ). Participants were then prompted to watch a mediatised video conveying negative messages. Immediately after viewing the video, participants indicated their degree of agreement with the messages conveyed they completed the Back-PAQ a second time and they indicated whether they intended to change their behavior as a result of watching the video. Changes in mean Back-PAQ score after viewing the video and the percentage of participants planning to protect their backs more were investigated. The influence of a history of LBP was also analysed. Results: 1338 participants were included. The initial mean Back-PAQ score was high (28.3 (SD 6)) and increased significantly after viewing the video (Cohen d: 0.42), indicating an increase in negative beliefs. This change was greater than the minimum detectable change (6.8) for 11.4% of participants. In total, 55% of respondents reported that they would protect their backs more after watching the video. Pain history did not influence the change in Back-PAQ score post viewing. Conclusions: This study demonstrates that a mediatized video which conveys negative messages about LBP reinforces LBP-related misbeliefs and may promote maladaptive behavior in a significant number of individuals. This study also confirms the prevalence of such misbeliefs in the general population and thereby, the necessity for clinicians to explore patients’ misbeliefs and their origin.