Abstract Background: Low back pain (LBP) is a symptomatology with a high global prevalence; health professionals, including physiotherapists, must have the skills to create professional actions that increase a quality of life for patients. Clinical simulation can be a pedagogic strategy that facilitates in students adequate training to acquire skills that improve professional reasoning in this clinical situation. The objective of this study was to compare the effects of clinical simulation with simulated patient (SP) versus simulation with role playing (RP) in physiotherapy students for decision-making in clinical skills while caring for a person with LBP. Methods . Experimental study, with 42 participants from two Colombian universities, randomized into two groups (SP n = 21, RP n = 21). The clinical skill was evaluated during the interaction with a person with LBP for which the Objective Structured Clinical Examination (OSCE-LBP) was validated for individuals with low back pain; thereafter, a pedagogical method was conducted that included clinical simulation and, finally, the OSCE-LBP was applied again to compare both groups. Results. Changes occurred in the OSCE-LBP among both groups of students: the scores increased (0.66 and 0.59 in RP and SP, respectively), and neither of the two was superior (difference 0.01 95%CI -0.21 to 0.23 ). Conclusion . Both types of simulation favour decision-making in professional reasoning in physiotherapy students during interaction with individuals with LBP. Contribution of paper: This is an RCT that explores the use of clinical simulation with simulated patient as a teaching method in decision making by physiotherapists versus traditional use of role playing