Chronic low back pain is one of the major health problems in the U.S., resulting in a large number of years of disability. To address the biopsychosocial nature of pain, interdisciplinary pain programs provide integrated interventions by an interdisciplinary team in a unified setting with unified goals. This study examined outcomes of an interdisciplinary program located at two sites with different staff, yet with a unified model of treatment and documentation. Efficacy at the combined sites was examined by comparing standard measures obtained upon admission to the program with measures at completion of a 3–4 week long program for 393 patients with chronic low back pain (CLBP). Repeated measures included pain severity, pain interference, efficacy of self-management strategies, hours of activity, depression, ability to do ADLs, and physical endurance. All repeated measures differed at the p < 0.001 level, with large effect sizes (0.66–0.85). Eighty-two percent of graduates reported being “very much improved” or “much improved”. A second analyses provided evidence that treatment effects were robust across sites with no differences (<0.001) found on five of seven selected outcome measures. A third analysis found that number of days of treatment was correlated on three of seven measures at the <0.01 level. However, the amount of variance explained by days of treatment was under 5% on even the most highly correlated measure. These finding are consistent with previous research and explore short-term effectiveness of treatment across treatment sites and with variable duration of treatment.