Objectives Cardiac troponins are sensitive and specific markers of myocardial injury. However, their reliability in renal disease has been questioned owing to possible renal involvement in troponin elimination. The primary objective of the present study was to examine whether serum cardiac troponin I is elevated in cats with compromised renal function and no clinically relevant structural cardiac disease. A secondary objective was to examine whether cardiac troponin I is measurable in the urine of cats with normal and compromised renal function. Methods This prospective case-control study included 52 cats (19 with compromised renal function, 19 with primary cardiac disease and 14 healthy controls). For all cats, clinical examination, echocardiography, electrocardiography, blood pressure, complete blood count, biochemistry, serum thyroxine and urinalysis were performed. Cardiac troponin I was measured in the serum and urine of each cat. Results Median (range) serum cardiac troponin I concentrations were 0.052 ng/ml (0.015–0.78 ng/ml) for the renal group, 0.083 ng/ml (0.003–3.27 ng/ml) for the cardiac group and 0.012 ng/ml (0.003–0.14 ng/ml) for the control group. The renal and cardiac groups both had significantly higher serum cardiac troponin I concentrations than the control group, whereas no difference could be detected between the renal and cardiac groups. In the renal group 7/19 cats had measurable urine cardiac troponin I, whereas cardiac troponin I was measurable in the urine of one cat in the cardiac group and two healthy controls. There was no significant correlation between serum and urine cardiac troponin I. Conclusions and relevance Elevated serum cardiac troponin I in cats with compromised renal function may occur without evidence of clinically relevant structural cardiac disease. Moreover, detecting cardiac troponin I in urine is most likely in cats with compromised renal function.