Liquid chromatography – tandem mass spectrometry (LC-MS/MS) has become the method of choice for many analytical applications due to its high selectivity and sensitivity as well as its suitability for a wide range of compounds in various sample matrices. With the legalization of cannabis for medical and recreational applications in Canada and in many States in the US, LC-MS/MS method has been applied for the analyses of pesticides and other toxic chemicals such as mycotoxins to control the quality of the cannabis products and to evaluate the risk of human exposure. In LC-MS/MS, target analytes in a sample were first separated from each other and from potential interfering components by liquid chromatography (LC) and then identified and quantified by tandem mass spectrometry (MS/MS) as compared with reference standards.