Objectives Feline osteoarthritis (OA) is a common, degenerative joint condition that is an important cause of chronic pain in cats. Cannabinoids have shown potential in reducing pain and inflammation in OA, but research in cats is limited. This study aimed to assess the safety and efficacy of a cannabidiol (CBD)/cannabidiol acid (CBDA) paste would in cats with OA. We hypothesised that CBD/CBDA paste would reduce pain scores and would be safe for use without significant adverse effects. Methods In this randomised, double-blinded, placebo-controlled crossover study, client-owned cats with OA were assigned to two study groups and received a 6-week course of both CBD/CBDA paste and a placebo. During the initial consultation and following appointments, cats underwent orthopaedic examination pain assessment with the North Carolina State University Translational Research in Pain (TRiP) Feline Musculoskeletal Pain Index scoring system and blood examination. Owners filled in a bi-weekly questionnaire (Dutch Orthopaedic Rating for Feline Osteoarthritis Pain, DORFOP). TRiP and DORFOP scores were analysed using mixed-effects models. Clinical chemistry in week 6 was compared using paired t -tests. Results A total of 26 cats participated in the study. Of these, 12 dropped out primarily because of their refusal to eat the CBD/CBDA paste, and, in some cases, vomiting was reported. Fourteen cats were left to complete the study. CBD/CBDA paste significantly reduced TRiP and DORFOP scores after 6 weeks of administration, with changes in DORFOP starting after 2 weeks. No differences in clinical biochemistry were observed between the placebo and CBD/CBDA paste at week 6. Conclusions and relevance CBA/CBDA paste effectively reduced pain in cats, but the high drop-out rate is concerning. Further research with larger sample sizes and longer treatment durations is needed to confirm these findings.