ObjectivesRadioiodine (I-131) therapy is the most appropriate treatment option for many hyperthyroid cats, as it is minimally invasive and often curative. Nevertheless, I-131 treatment is not always pursued by owners. Hence, it is important to obtain more insight into owner satisfaction during and after I-131 treatment, and their decision-making process. In this study, we describe the characteristics of owners and their hyperthyroid cats referred for I-131 therapy, and determine owners' motivation and how they experienced the I-131 treatment of their cat. MethodsA survey was sent to owners whose cats underwent I-131 therapy (n = 1071) between 2010 and 2017 at Ghent University. The survey contained 35 questions with tick-box or free-text answer options concerning family situation, pet insurance, previous therapy, comorbidities, motivation for I-131 therapy and owner perception of this treatment. ResultsIn total, 438 owners completed 94% or more of the questionnaire. Over half of the cats (55%) had received previous medical, dietary or surgical treatment. Motivations for changing the initial therapy to I-131 therapy included difficulties in administering medication (31%), insufficient improvement in clinical signs (23%), side effects (16%) and following the referring veterinarian's advice (16%). Almost a fifth of owners (18%) were not informed about the existence of I-131 therapy by their veterinarian and found information on I-131 treatment online or through friends. Hospitalising their cat was very distressing for 17% of owners. Most owners (92%) were satisfied with the treatment. Reasons for dissatisfaction were insufficient communication, iatrogenic hypothyroidism, persistent hyperthyroidism and comorbidities post-treatment. Conclusions and relevanceOur study stresses the importance of communication regarding the possible outcome of I-131 treatment, the importance of managing underlying comorbidities before treatment and anticipating the stress of owners during their cat's hospitalisation period. The results of this study could help in improving client communication when advising on I-131 treatment.