Cannabidiol is a phytocannabinoid with proven pharmacological properties that is also used in the cosmetic industry for its sebostatic and antioxidant activities, being considered a new anti-aging ally. An analytical method is proposed for the determination of CBD in cosmetic products by liquid chromatography with tandem mass spectrometry, after leaching the CBD from the cosmetic matrix with ethanol. Low instrumental limits of detection (0.22 ng mL−1) and quantification (0.74 ng mL−1) allow the determination of CBD at trace levels without needing preconcentration, whereas the wide linearity of the method allows the determination of CBD in more concentrated samples without high dilution. The method was successfully applied to the analysis of six cosmetic products and a raw material. The proposed method is suitable for the quality control of cosmetic products containing CBD, being able to quickly and easily determine this compound, ensuring that its concentration in the finished product is the desired one.