Cognitive behavioral therapy for chronic pain (CBT-CP) has a strong evidence base, but little is known about when treatment benefits are achieved. The current study is a secondary analysis of individuals with chronic back pain recruited for a non-inferiority trial comparing interactive voice response (IVR) CBT-CP versus in-person CBT-CP. Using data from daily IVR surveys, a clinically meaningful change was defined as a 30% reduction in pain intensity (n = 108) or 45% increase in daily steps (n = 104) compared to baseline week. We identified individuals who achieved a meaningful change at any point during treatment, then we compared those who maintained a meaningful change in their final treatment week (i.e., responders) to those who did not or achieved a meaningful change but lapsed (i.e., non-responders). During treatment, 46% of participants achieved a clinically meaningful decrease in pain intensity, and 66% achieved a clinically significant increase in number of steps per day. A total of 54% of patients were classified as responders in terms of decreases in pain intensity, and 70% were responders in terms of increases in step count. Survival analyses found that 50% of responders first achieved a clinically meaningful change by week 4 for pain intensity and week 2 for daily steps. Dropout and demographic variables were unrelated to responder status and there was low agreement between the two measures of treatment response. Collectively, results suggest that most responders improve within 4 weeks. Evaluating treatment response is highly specific to the outcome measure with little correlation across outcomes.