Recent studies have suggested that the deadlift exercise may be effective in reducing pain intensity and increasing activity for most, but not all, patients with a dominating mechanical low back pain pattern. This study’s goal was to evaluate which individual factors measured at baseline could predict activity, disability, and pain intensity in patients with mechanical low back pain after an 8-week training period involving the deadlift as a rehabilitative exercise. Thirty-five participants performed deadlift training under the supervision of a physical therapist with powerlifting experience. Measures of pain-related fear of movement, hip and trunk muscle endurance and lumbopelvic movement control were collected at baseline. Measures of activity, disability and pain intensity were collected at baseline and at follow-up. Linear regression analyses were employed to create models to predict activity, disability and pain intensity at follow-up. Results displayed that participants with less disability, less pain intensity and higher performance on the Biering-Sørensen test, which tests the endurance of hip and back extensor muscles, at baseline benefit from deadlift training. The Biering-Sørensen test was the strongest predictor since it was included in all predictive models. Pain intensity was the next best predictor as it was included in two predictive models. Thus, for strength and conditioning professionals who use the deadlift as a rehabilitative exercise for individuals with mechanical low back pain, it is important to ensure that clients have adequate back extensor strength and endurance and a adequately low pain intensity level to benefit from training involving the deadlift exercise.