["Personal Relationships, Volume 33, Issue 3, September 2026. ", "\nABSTRACT\nCommitment predicts key outcomes such as stay–leave decisions, willingness to sacrifice, and infidelity. Given its central role in relationship research, it is essential that commitment measures be valid and reliable across cultural contexts. We examined the construct and convergent validity and measurement invariance of two commitment measures—the Investment Model Scale (IMS) and Measurement of Components of Commitment Scale (MCCS)—across Iranian (N = 189) and Canadian (N = 240) samples. Our results indicated that the IMS is a valid and reliable measure in both samples and is associated with related constructs, for example, inclusion of other in the self, in the expected direction. Measurement invariance results further showed that the IMS can be used for cross‐cultural comparisons of commitment and its predictors. The MCCS also demonstrated a comparable factor structure across cultures but required substantial modifications, revealing conceptual and methodological limitations. Nevertheless, its multidimensional approach reflects a culturally sensitive perspective that incorporates moral, social, and structural influences on commitment. These findings highlight the strengths of existing measures and underscore the need for a more robust, culturally sensitive multidimensional assessment of commitment.\n"]