Technological advances, such as radio-telemetry, have been increasingly employed for animal monitoring because they can furnish important information regarding the ecology and behaviour of various species. However, during a study on semi-domiciled domestic cats (Felis silvestris catus)conducted in an environmental protection area in Ilha Comprida, state of São Paulo, Brazil, we identified a case of dermatitis that was caused by a radio-collar, which was first noticed by the pet owner. This provided the opportunity for close observation not normally possible when these are used to track animals in the wild. It is our aim to bring the possibility that skin inflammation may develop when using radio-collars in radio-telemetry monitoring to the attention of other researchers. This finding highlights the need for greater attention to be paid to the use of this methodology, especially in the realm of wild animals.