Background: Cardiac troponin I (cTnI) is a sensitive and specific marker of acute cardiac damage. We examined the prevalence, characteristics and outcome of incidental cTnI rises in older patients. Methods: One hundred and eighty-seven consecutive patients aged 65 years or over with a raised cTnI on admission at least 8 h after symptom onset were categorised into: (1) ST-elevation myocardial infarction, (2) other acute coronary syndromes (ACS), (3) other recognised non-ACS causes of cTnI rise and (4) non-ACS with no other identifiable cause (an incidental finding). The number of readmissions and deaths for each group was measured at 30 and 90 days. Results: Age range = 65–98 years. Male = 55.6%. Fifty-four percent had a raised cTnI due to non-ACS illnesses, whilst in 18% it was an incidental finding. The latter group was relatively older and had a significantly lower degree of cTnI rise (U = 1718.5, p = 0.002), but a higher readmission and mortality rate compared to the other groups (categories 1–3) for both follow-up periods. Conclusions: Incidental cTnI rise is common in older patients and is associated with a poorer prognosis compared to ACS or a recognised non-ACS condition. Future research should attempt to evaluate the significance of such incidental rises in elderly patients.