Young men are important targets in HIV prevention in Tanzania and throughout sub-Saharan Africa. Anxiety and depression are common among youth and may be important predictors of HIV risk behaviors; evidence of these relationships in high-risk populations is needed. Using baseline and 1 year follow-up assessments from an HIV prevention trial we assessed the association between changes in symptoms of anxiety and depression and follow-up sexual risk behaviors (condom use and sexual partner concurrency) controlling for baseline sexual risk behaviors among 1113 male members of social groups known as "camps" in Dar es Salaam, Tanzania. Anxiety and depression were measured using the HSCL-25 and condom use and sexual partner concurrency were assessed through self-report. In separate models, increases in anxiety and depression were associated with sexual partner concurrency and with lower levels of condom use. In a combined model, both anxiety and depression appeared to independently affect concurrency but only depression was independently associated with condom use, with the association between anxiety and condom use being likely attributable to covariance with depression symptoms. The results of this study indicate the importance of screening and providing treatment for depression and anxiety disorders in high HIV-prevalence contexts, and the need to develop effective HIV prevention interventions targeting young men living with anxiety and depression.