Prior studies evaluating predictors of pain-related outcomes following treatment for sciatica have been limited by methodological problems, including retrospective study design, use of unvalidated outcome measures, and short-term follow-up periods. Despite these limitations, some reports have suggested that symptoms of psychological distress may predict individual differences in pain treatment-related outcomes (e.g., higher levels of depressive and anxious symptomatology are associated with greater pain and disability after treatment). In this study, we sought to determine whether acute symptoms of depression and anxiety were prospectively associated with treatment outcomes over a 3-year follow-up period in surgically treated and non-surgically treated patients with sciatica. Patients were recruited from the practices of community-based physicians throughout the state of Maine, and underwent in-person baseline assessments, with mailed follow-up questionnaires at 3, 6, 12, 24, and 36 months. Study outcomes included patient-reported symptoms of pain and disability. For each outcome variable, we examined whether baseline mood (i.e., mood assessed prior to the initiation of treatment), as well as mood at the immediately preceding assessment point, prospectively predicted outcomes over 3 years in multivariate repeated-measures analyses. In most analyses, symptoms of depression and anxiety, both at baseline and at the preceding time point, were significant independent predictors of worse pain and function after controlling for relevant covariates. Collectively, elevated distress appears to be a significant risk factor for reduced treatment benefit (i.e., less improvement in pain and disability) over short and medium-term follow-up periods in patients with sciatica. Future research should determine whether the prospective identification and treatment of patients with high levels of distress (a "yellow flag") is associated with improved treatment outcomes.