Background The clinical course of acute low back pain (LBP) is generally favourable; however, there is significant variability in the prognosis of these patients. A clinical prediction model to predict the likelihood of pain recovery at three time points for patients with acute LBP has recently been developed. The aim of this study is to conduct a broad validation test of this clinical prediction model, by testing its performance in a new sample of patients and a different setting.Methods The validation study with a prospective cohort design will recruit 420 patients with recent onset non-specific acute LBP, with moderate pain intensity, seeking care in the emergency departments of hospitals in São Paulo, Brazil. The primary outcome measure will be days to recovery from pain. The predicted probability of pain recovery for each individual will be computed based on predictions of the development model and this will be used to test the performance (calibration and discrimination) in the validation dataset.Discussion The findings of this study will better inform about the performance of the clinical prediction model, helping both clinicians and patients. If the model’s performance is acceptable, then future research should evaluate the impact of the prediction model, assessing whether it produces a change in clinicians’ behaviour and/or an improvement in patient outcomes.Ethics and dissemination Ethics were granted by the Research Ethics Committee of the Universidade Cidade de São Paulo, #20310419.4.0000.0064. Study findings will be disseminated widely through peer-reviewed publications and conference presentations.