Background: Low back pain (LBP) is a global public health challenge, which causes high healthcare costs and the highest burden on society in terms of years lived with disability. While patients’ expectations for improvement may have effects on LBP treatment outcomes, it remains unclear if psychological profiles modify this relationship. Therefore, the objectives of this study were to investigate if (a) patients’ expectations predicted short-term outcome, and (b) psychological profile, pain intensity and self-rated health modified the relationship between expectations and outcome. Methods: Data were collected between April 2012 and January 2016 during the inclusion into a randomized controlled trial. Potentially eligible participants were identified through 40 chiropractic clinics located across Sweden. Patients’ expectations, psychological profile, pain intensity, activity limitation and self-rated health were collected from patients with recurrent persistent LBP during their first chiropractic visit (n = 593). Subjective improvement was measured at the fourth visit. Results: Patients with a high expectation of improvement had 58% higher risk to report an improvement at the fourth visit (RR = 1.58, 95% CI: 1.28, 1.95). Controlling for potential confounders only slightly decreased the strength of this association (RR = 1.49, 95% CI: 1.20, 1.86). Baseline pain intensity, psychological profile and self-rated health did not modify the effect of expectation on outcome. Conclusions: Baseline patients’ expectations play an important role when predicting LBP treatment outcomes. Clinicians should consider and address patients’ expectations at the first visit to best inform prognosis. Significance: This study confirms the importance of patients’ expectations in a clinical setting. Patients’ expectations predict the short-term outcome of chiropractic care for LBP. Pain intensity, psychological profile and self-rated health did not modify this relationship.