Introduction: Whether early antiretroviral therapy (ART) initiation could impact sexual risk behaviours remains to be documented. We aimed to investigate changes in sexual behaviours within the 24 months following an early versus standard ART initiation in HIV-positive adults with high CD4 counts. Methods: We used data from a prospective behavioural study nested in a randomized controlled trial of early ART (Temprano-ANRS12136). Time trends in sexual behaviours from enrolment in the trial (M0) to 12-month (M12) and 24-month (M24) visits were measured and compared, using Generalized Estimating Equations models, between participants randomly assigned either to initiate ART immediately (early ART) or to defer ART initiation until on-going WHO starting criteria are met (standard ART). Indicators of sexual behaviours included 1) sexual activity in the past year, 2) multiple partnership in the past year, 3) unprotected sex at last intercourse and 4) risky sex (i.e. unprotected sex with a partner of HIV negative/unknown status) at last intercourse. Results: Analyses included 1952 participants (975 with early ART and 977 with standard ART; overall median baseline CD4 count: 469/mm(3)). Among participants with early ART, significant decreases were found between M0 and M24 in sexual activity (Odds Ratio [OR] 0.72, 95% Confidence Interval [95% CI] 0.57-0.92), multiple partnership (OR 0.57, 95% CI 0.41-0.79), unprotected sex (OR 0.59, 95% CI 0.47-0.75) and risky sex (OR 0.58, 95% CI 0.45-0.76). Among participants with standard ART, sexual behaviours showed similar trends over time. These decreases mostly occurred within the 12 months following enrolment in the trial in both groups and prior to ART initiation in participants with standard ART. For unprotected sex and risky sex, decreases were or tended to be more pronounced among patients reporting that their last sexual partner was non-cohabiting. Conclusions: In these sub-Saharan adults with high CD4 counts, entry into HIV care, rather than ART initiation, resulted in decreased sexual activity and risky sexual behaviours. We did not observe any evidence of a risk compensation phenomenon associated with early ART initiation. These results illustrate the potential behavioural preventive effect of early entry into care, which goes hand in hand with early ART initiation.