Resumen: Low back pain is a global health problem, and its level of disability depends, among other variables, on patients' negative beliefs regarding pain. Evidence supports that these beliefs are associated with those held by their treating professionals, so it is important to identify how they evolve during the undergraduate training of health professionals. This cross-sectional study aimed to determine the presence of negative beliefs about low back pain in physical therapy students and compare them between different courses of the training cycle. Second, to fifth-year physiotherapy students from a Chilean university participated; they completed a survey based on Deyo's seven myths about low back pain and responded according to their degree of agreement with the statements. The results were compared between the different levels. 127 students completed the survey (57 males and 70 females). Myths 1, 2, 4, 6, and 7 were presented more frequently in the second year and tended to decrease progressively in higher grades. Myths 3 and 5 presented a less clear distributional pattern. Second-level students presented a higher degree of agreement with the myths, and third-level students presented greater insecurity in the answers. In contrast, fourth and fifth-level students presented greater disagreement with the myths. In conclusion, negative beliefs about low back pain may be present in physical therapy students, but these tend to modify positively throughout their formative process.