Numerous randomised controlled trials have evaluated the outcomes of internet-delivered psychological pain management programs (PMPs) as a way of increasing access to care for people with chronic pain. However, there are few reports of the effectiveness of these PMPs when provided as part of routine care. The present study sought to report the clinical and demographic characteristics of users (n = 1,367), and examine the effectiveness of an established internet-delivered psychological PMP program in improving several pain-related outcomes, when offered at a national digital mental health service over a 5-year period. It also sought to comprehensively explore predictors of treatment commencement, treatment completion, and clinical improvement. Evidence of clinical improvements (% improvement; Hedges g) in all outcomes, including pain interference (18.9%; 0.55), depression (26.1%; 0.50), anxiety (23.9%; 0.39), pain intensity (12.8%; 0.41), pain self-efficacy (-23.8%; -0.46) and pain-catastrophising (26.3%; 0.56), were found. A small proportion of users enrolled but did not commence treatment (13%), however high levels of treatment completion (whole treatment = 63%; majority of the treatment = 75%) and satisfaction (very satisfied = 45%; satisfied = 37%) were observed among those who commenced treatment. There were a number of demographic and clinical factors associated with commencement, completion and improvement, but no decisive or dominant predictors were observed. These findings highlight the effectiveness and acceptability of internet-delivered psychological PMPs in routine care, and point to the need to consider how best to integrate these interventions into the pathways of care for people with chronic pain.