Abstract Objectives Evidence for the comparative cost-effectiveness of intra-articular corticosteroid injection in people with hip osteoarthritis (OA) remains unclear. This study investigated the cost-effectiveness of best current treatment (BCT), comprising advice and education, with BCT plus a single ultrasound-guided intra-articular hip injection of 40 mg triamcinolone acetonide and 4 ml 1% lidocaine hydrochloride (BCT+US-T). Methods A trial-based cost–utility analysis of BCT+US-T compared with BCT was undertaken over 6 months. Patient-level cost data were obtained, and effectiveness was measured in terms of quality-adjusted life years (QALYs), allowing the calculation of cost per QALY gained from a UK National Health Service (NHS) perspective. Results BCT+US-T was associated with lower mean NHS costs (BCT+US-T minus BCT: −£161.6; 95% CI: −£583.95, £54.18) and small but significantly higher mean QALYs than BCT alone over 6 months (BCT+US-T minus BCT: 0.0487; 95% CI: 0.0091, 0.0886). In the base case, BCT+US-T was the most cost-effective and dominated BCT alone. Differences in total costs were driven by number of visits to NHS consultants, private physiotherapists and chiropractors, and hip surgery, which were more common with BCT alone than BCT+US-T. Conclusion Intra-articular corticosteroid injection plus BCT (BCT+US-T) for patients with hip OA results in lower costs and better outcomes, and is highly cost-effective, compared with BCT alone. Trial registration EudraCT: 2014-003412-37 (8 August 2015) and registered with Current Controlled Trials: ISRCTN 50550256 (28 July 2015). Trial protocol Full details of the trial protocol can be found in the Supplementary Appendix, available with the full text of this article at https://bmcmusculoskeletdisord.biomedcentral.com/articles/10.1186/s12891-018-2153-0, doi: doi.org/10.1186/s12891-018-2153-0.