Companion animals have been considered, for centuries, as humans’ best friends. Most of our pets are really our best friends, as they are faithful, make as company and love us unconditionally. They also share our environment, living inside our houses being therefore exposed to the same indoor contaminants. As is it well known, humans and animals are frequently exposed to harmful chemicals, including metals that may induce deleterious effects, as for example DNA damage. In the present work, the levels and potential effects of indoor contaminants in companion animals were evaluated and the implications of using pets as sentinels for human exposure discussed.