Objective To evaluate the effectiveness of Δ9-tetrahydrocannabinol (dronabinol, DRO), as an add-on treatment in patients with refractory chronic pain (CP). Methods An exploratory retrospective analysis of 12-week data provided by the German Pain e-Registry (GPeR) on adult patients with treatment refractory CP who received DRO. Results Between March 10, 2017 and June 30, 2019 the GPeR collected information on 89,095 pain patients of whom 1,145 patients (1.3%; 53.8% female, mean ± SD age: 56.9 ± 10.6 years) received DRO, and 70.0% documented use for the entire 12-week evaluation period. Average DRO daily dose was 15.8±7.5mg, typically in three divided doses (average DRO dose of 5.3±2.1mg). Average 24-hr. pain intensity decreased from 46.3±16.1 to 26.8±18.7 mm VAS, (absolute VAS difference -19.5 ± 17.3; p < 0.001). A 50% improvement from baseline was documented among patients who completed follow up for pain (46.5%), activities of daily living (ADL) (39%), quality-of-life (QoL) (31.4%), and sleep (35.3%). A total of 536 patients (46.8%) reported at least one of 1617 drug related adverse events (DRAEs), of which none was serious, and 248 (21.7%) stopped treatment. Over the 12-week period, 59.0% of patients reported a reduction of other pain treatments and 7.8% a complete cessation of any other pharmacological pain treatments. Conclusion Add-on treatment with DRO in patients with refractory CP was well tolerated and associated with a significant improvement.