The authors describe the development of the Gender Identity Reflection and Rumination Scale (GRRS), which measures rumination in the context of gender identity among transgender persons. GRRS items were formulated taking into account previous research on rumination, stigma stress, and identity processing. Two national U.S. samples were collected to investigate the psychometric properties of the GRRS, resulting in 3 factors of gender identity rumination: Reflection, Rumination, and Preoccupation With Others’ Perceptions.