To examine the impact of migration and acculturation of Turkish men who have sex with men (MSM) to Germany, using data from the European MSM Internet Survey (EMIS-2010), on measures of acculturation including circumcision status, internalized homonegativity (IH), HIV/STI knowledge, sexual orientation, outness, HIV-testing, and sexual behaviors. We compared four groups of MSM: MSM born and residing in Germany who had completed the questionnaire in German (n = 38,915), MSM born and residing in Germany, with a father or mother born in Turkey (n = 97), MSM residing in Germany who were born in Turkey or whose parents were born in Turkey (n = 262), and MSM who were born and residing in Turkey and who completed the questionnaire in Turkish (n = 1,717). Data showed that there were significant dose–response curves between level of migration and several outcome variables. As exposure to Germany increased, MSM had lower IH, higher HIV/STI knowledge, increased outness, and were less likely to be circumcised. There were similar significant findings with regard to sexual HIV risk behavior (condomless anal intercourse with partners of unknown (or sero-discordant) HIV status). Data were consistent with acculturation over generations in immigrant groups in MSM migrating from Turkey to Germany. Integration includes both cultural aspects (circumcision) and integration into a more homopositive gay environment (IH, outness, increased HIV/STI knowledge), and sexual HIV risk behavior. Migration and associated acculturation may constitute a risk change for HIV/STI and mental health issues associated with IH and outness.