Once recognized as the most severe in Europe, the HIV epidemic in Ukraine is concentrated among people who inject drugs, men who have sex with men, and female sex workers. Integrated biobehavioral surveys, as a part of the second generation surveillance, are used to monitor HIV infection trends in key populations since 2002. The present paper is focused on the analysis of HIV prevalence trends in four nationally representative rounds of integrated biobehavioral surveys from 2008/9, 2011, 2013, and 2015 in people who inject drugs, men who have sex with men, and female sex workers. Between 2008/9 and 2015, the HIV prevalence has decreased significantly in people who inject drugs (24.2 to 22.0%) and female sex workers (13.6 to 6.3%), while the change in men who have sex with men was not significant (8.5 to 7.8%). There was a significant increase in people who inject drugs and men who have sex with men between 2013 and 2015. In subgroups younger than 25 years, prevalence increased more than twofold in men who have sex with men (1.9 to 4.3%), with no changes in people who inject drugs and female sex workers. The observed decline in prevalence, especially in young subgroups, may result from the effect of extensive prevention efforts on drug injection-related transmission. Recent increase in young men who have sex with men may be a sign of a new wave of the epidemic in this group.