Radioactivity from naturally occurring radioactive materials (NORMs) are potentially harmful to human health. Regulation and quality control of NORMs are important to prevent hazards from these materials. Certified reference materials (CRMs) of NORMs are typically certified for radioactivity of the constituent elements using alpha spectrometry. However, the mass fractions of the radioactive elements are indirectly obtained by conversion of the radioactivity data using specific activities. In this study, we measured the mass fractions of radioactive elements uranium and thorium in environmental samples zircon, bauxite, and phosphogypsum and compared the results obtained using alpha spectrometry. As the unavailability of isotopically enriched materials prohibits the use of isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS), standard addition was used to determine the mass fractions in the samples using ICP-MS. The samples were processed by alkali fusion employing lithium tetraborate/lithium bromide flux and recovered in dilute nitric acid. Standard uranium and thorium solutions were spiked into the sample solutions by appropriate amounts along with thalium as an internal standard, resulting in ten measurement solutions. The determined mass fractions of uranium and thorium were 0.9–300 mg kg-1, and the expanded uncertainties (at a 95% level of confidence) were estimated to be less than 3.4%. Good agreement was observed between the values from ICP-MS and alpha spectrometry, supporting the validity of the measurement results. The analytical procedure developed in this study is expected to be a basis of future research for certification of radioactive elements in NORMs.