(1) Background: Clays are popular raw materials of natural origin used in cosmetology, beauty salons, and home care. They have moisturizing, soothing, cleansing, disinfecting, detoxifying, and regenerating properties, and can be used externally in the form of poultices or internally in solution form. Though they are characterized by a rich and diverse mineral composition and are considered safe for the body, their use can expose users to harmful elements including mercury. (2) Materials and methods: This study analyzed mercury (Hg) concentrations in samples of cosmetic clays available on the Polish market. Hg analysis was performed using the AAS method with an AMA 254 analyzer. The clays differed in type/color and were purchased from different manufacturers. (3) Results: The mean Hg content in all the tested samples was 28.91 µg/kg, with a range of changes of 1.87-200.81 µg/kg. The highest concentrations of Hg were found in green (AM = 53.26 µg/kg) and white (AM = 52.80 µg/kg) clays, while the lowest were detected in purple (AM = 2.56 µg/kg) and blue (AM = 3.69 µg/kg) clays. The differences in Hg content between individual types of clay were statistically significant. (4) Conclusions: Due to the presence of Hg found in all the samples of cosmetic clay tested, it is likely that these products need to be tested for their metal contents.