This study presents a method for the reliable determination of 87Sr/86Sr in food grains, which are characterized by low Sr concentrations but high concentration ratios of Rb/Sr and K/Sr using multi‐collector inductively coupled plasma mass spectrometry (MC-ICP-MS). The Sr/matrix separation procedure using Sr resin was optimized for a standard reference material of wheat flour (NIST SRM 1567b). Consequently, a high Sr recovery (97.0 % ± 1.2 %, mean ± 1 SD, n = 7) and effective Sr/matrix separation (e.g., 85Rb/88Sr intensity ratio at MC-ICP-MS measurements × 100 of 0.00014 % ± 0.00003 %, mean ± 1 SD, n = 7) were achieved. Furthermore, potential spectroscopic interferences caused by matrix ions were estimated by analyzing NIST SRM 987 solutions spiked with varying amounts of Rb or Ca using MC-ICP-MS. The proposed method was validated by analyzing eight standard reference materials of vegetal, animal, and geological origins studied previously, yielding 87Sr/86Sr ratios consistent with literature values, which demonstrates the applicability of the method across diverse sample matrices. Finally, the proposed method was applied to standard reference materials for which 87Sr/86Sr ratios are not reported to our knowledge (NIST SRM 1567a and b wheat flour). The 87Sr/86Sr ratios of NIST SRM 1567a and b were estimated to be 0.70895 ± 0.00005 (2 SD, n = 34), and 0.70898 ± 0.00003 (2 SD, n = 25), respectively.