Muscularity bias internalization (MBI) refers to one's beliefs in negative muscularity-based stereotypes and negative self-evaluations due to muscularity. Empirical research shows that MBI significantly correlates with muscularity-oriented eating and body image disturbances. The Muscularity Bias Internalization Scale (MBIS) measures MBI and has been validated in general adult populations. Given that evidence supports a higher risk of eating and body image disturbances in Transgender and Gender-Diverse (TGD) people compared to their cisgender counterparts, validating the MBIS in TGD people is essential to further clarifying disparities in eating and body image disturbances in this population. With a sample of 410 Chinese TGD adults, exploratory and confirmatory factor analyses supported a two-factor structure. Comparisons of the second-order and bifactor models favored the second-order model. The MBIS showed good internal consistency and sound construct validity. Strong measurement invariance was confirmed across transgender men, transgender women, and gender-diverse groups, suggesting that these groups interpreted the MBIS similarly and that conclusions of differences in MBI across TGD adults can be considered true group differences. Specifically, transgender men reported the highest MBIS scores, followed by gender-diverse individuals, and then transgender women. These findings suggested that the MBIS appears to be a psychometrically sound instrument of MBI in Chinese TGD adults.