This paper is the first in mainland Tanzania to report on sexual practices and HIV perceived risk of Men who have Sex with Men (MSM). A total of 150 MSM with a mean age of 21.3 were recruited using a respondent-driven sampling. Their median age at first anal sex was 12.2 and their median number of lifetime sexual partners was 35. The majority (94.0%) of the respondents reported more than two sex partners in the three months preceding the survey, and 32.0% reported involvement in heterosexual relationships. Two-thirds of the participants had low HIV perceived risk, which was associated with involvement in heterosexual relationships (AOR, 3.6, 95% CI: 1.0­ 15.0), lower condom use (AOR, 0.3, 95% CI: 0.2-0.7), alcohol consumption (AOR, 6.0, 95% CI: 2.3-16.9) and lower likelihood of ever having been tested for HIV (AOR, 0.3, 95% CI: 0.1-0.9). Focuses in HIV prevention have excluded MSM and our results indicate the need to consider this group in HIV programming in Tanzania.