Increasing HIV testing frequency in gay and bisexual men (GBM) is critical to reducing the time between HIV infection and diagnosis. Using anonymous national behavioural surveillance data (2013-2018) from 43,753 surveys of Australian GBM, we examined HIV testing frequency trends and factors differentiating PrEP-users, non-PrEP-users reporting two or more tests in the previous year, and non-PrEP-users reporting less frequent testing. The proportion tested at least annually increased from 64.4% in 2013 to 70.8% in 2018 (p-trend < 0.001), and from 73.9% to 84.6% among the 51.6% of men classified as higher-risk. Among higher-risk men, having two or more tests in the previous year increased from 48.0% to 69.3% (p-trend < 0.001). Among higher-risk non-PrEP-users, it increased from 47.2% to 54.8% (p-trend < 0.001), however, there was a decrease since 2016 (p-trend < 0.001). Among PrEP-users, it increased from 82.1% in 2013 to 97.3% in 2018 (p-trend < 0.001). Non-PrEP-using higher-risk men having less frequent tests reported lower risk than PrEP-users and non-PrEP-using men reporting two or more tests in the previous year. However, recent risk behaviour was not uncommon: nearly half reported condomless sex; one-fifth reported receptive condomless sex with ejaculation; over half reported group sex; one-quarter used drugs for the purposes of sex; and one-fifth had more than ten sex partners. Efforts are needed to encourage frequent testing and PrEP use among non-PrEP-users who are at higher-risk.