Use of crystal methamphetamine (crystal) among gay and bisexual men (GBM) has been associated with condomless anal intercourse with casual partners (CLAIC) and HIV infection. Pre-exposure prophylaxis (PrEP) and undetectable viral load (UVL) are important biomedical HIV prevention strategies. We investigate the relationship between crystal use and HIV sexual risk behaviours in the context of PrEP and UVL. In 2018, 1367 GBM provided details about crystal use and HIV prevention strategies. Binary logistic regression was used to estimate associations between crystal use and behaviour. Recent crystal use was independently associated with greater social engagement with gay men and having more sexual partners. Crystal use was also independently associated with use of PrEP and UVL among GBM who engaged in CLAIC. Although GBM who used crystal were more likely to have engaged in CLAIC, they were also more likely to use biomedical HIV prevention which mitigates against the risks of HIV infection.