We surveyed Australian gay and bisexual men, assessing belief in HIV treatment as prevention (TasP) and support for early treatment. We identified the characteristics of participants who believed in TasP and supported early treatment using multivariate logistic regression. In 2013, 1316 men participated; 1251 participated in 2015. Belief in TasP increased from 2.6 % in 2013 to 13.1 % in 2015 (p < 0.001). The increase was most noticeable among HIV-positive men (from 9.7 % to 46.2 %). Support for early treatment increased from 71.8 % to 75.3 % (p = 0.02). Belief in TasP was associated with being HIV-positive, having a tertiary education, having recent condomless anal intercourse with casual male partners, and ever having taken post-exposure prophylaxis. Support for early HIV treatment was associated with being younger, living in New South Wales and being in paid employment. We recommend continued monitoring of the growing gap in belief about TasP between HIV-positive men and HIV-negative/untested men.