Chronic pain is both prevalent and debilitating. It is often treated with interdisciplinary pain rehabilitation programs (IPRPs). While research has largely focused on the effectiveness of IPRPs in improving patient outcomes, negative treatment effects remain under-explored. This study aims to investigate both the prevalence and types of negative outcomes following IPRPs for chronic pain. Data for the current study were obtained from the Swedish Quality Registry for Pain, with 22771 patients undergoing IPRPs between 2016 and 2023. We calculated the Reliable Change Index to find reliable deterioration across 18 patient-reported outcome measures, including pain intensity, physical function, psychological well-being, and vitality. Descriptive statistics were employed to determine the prevalence of deterioration, the prevalence of less severe deterioration, and the frequency of multiple deteriorations per patient. Results showed that while most participants did not report any areas of deterioration, about 23% of patients did experience reliable deterioration on at least one measure at the end of rehabilitation. Deterioration was most frequent in measures assessing physical status and pain, while psychological measures showed less deterioration. Mild deterioration on at least one measure was observed in 44.5% of patients. This study shows that a substantial proportion of patients experience at least some negative short-term outcomes following IPRPs, primarily in physical and pain-related outcomes. The findings underscore the importance of acknowledging and further investigating negative outcomes in chronic pain rehabilitation, and to take measures to address this issue.