Sexual and gender identity have frequently been assessed in public health research as static states. However, a substantial and growing body of evidence indicates that both identities may have greater potential for change over time than once supposed. Despite this evidence, research into adult identity change remains relatively limited. Using longitudinal data from 1553 Black men who have sex with men (BMSM) aged 18-68 years and recruited from study locations in six major cities across the country, we examined changes in sexual and gender identities over a period of 12 months. The results showed that sexual and gender identity did indeed change among adult BMSM. Additionally, we explored internalized homophobia (IH) as a potential driver of identity change and found that IH significantly impacts the degree and direction of change, with individuals who reported higher baseline IH more likely to demonstrate a shift toward a heterosexual/straight identity at 6 and 12 months. The results are discussed in light of what is known and unknown regarding identity change, and potential avenues for future research are explored.