Abstract Introduction Key populations including female sex workers (FSW) and men who have sex with men (MSM) bear a disproportionate burden ofHIV. However, the role of focusing prevention efforts on these groups for reducing a country'sHIVepidemic is debated. We estimate the extent to whichHIVtransmission amongFSWandMSMcontributes to overallHIVtransmission in Dakar, Senegal, using a dynamic assessment of the population attributable fraction (PAF). Methods A dynamic transmission model ofHIVamongFSW, their clients,MSMand the lower‐risk adult population was parameterized and calibrated within a Bayesian framework using setting‐specific demographic, behavioural,HIVepidemiological and antiretroviral treatment (ART) coverage data for 1985 to 2015. We used the model to estimate the 10‐yearPAFof commercial sex betweenFSWand their clients, and sex between men, to overallHIVtransmission (defined as the percentage of new infections prevented when these modes of transmission are removed). In addition, we estimated the prevention benefits associated with historical increases in condom use andARTuptake, and impact of further increases in prevention and treatment. Results The model projections suggest that unprotected sex between men contributed to 42% (2.5 to 97.5th percentile range 24 to 59%) of transmissions between 1995 and 2005, increasing to 64% (37 to 79%) from 2015 to 2025. The 10‐yearPAFof commercial sex is smaller, diminishing from 21% (7 to 39%) in 1995 to 14% (5 to 35%) in 2015. WithoutART, 49% (32 to 71%) moreHIVinfections would have occurred since 2000, whenARTwas initiated, whereas without condom use since 1985, 67% (27 to 179%) moreHIVinfections would have occurred, and the overallHIVprevalence would have been 60% (29 to 211%) greater than what it is now. Further large decreases inHIVincidence (68%) can be achieved by scaling upARTinMSMto 74% coverage and reducing their susceptibility toHIVby two‐thirds through any prevention modality. Conclusions Unprotected sex between men may be an important contributor toHIVtransmission in Dakar, due to suboptimal coverage of evidence‐informed interventions. Although existing interventions have effectively reducedHIVtransmission among adults, it is crucial that further strategies address the unmet need amongMSM.