Background There is growing interest in novel sexually transmissible infection (STI) prevention strategies, including doxycycline postexposure prophylaxis (doxy-PEP). We assessed interest in doxy-PEP and other STI prevention strategies among gay and bisexual men and nonbinary people in Australia, as well as prior antibiotic use for STI prevention, and knowledge of antimicrobial resistance (AMR). Methods We conducted a national, online survey in June to July 2023. Multivariable logistic regression was used to identify factors associated with the acceptability of doxy-PEP. Results Of 2046 participants, 26.9% had been diagnosed with an STI in the previous year. Condoms were rated as an acceptable STI prevention strategy by 45.1% of the sample, STI preexposure prophylaxis by 54.0%, and doxy-PEP by 75.8%. Previous antibiotic use for STI prevention was reported by 7.5% of the sample, and 2.6% were currently using antibiotics for STI prevention. Over half the sample (62.1%) had some knowledge of AMR. Of those who knew something about AMR, 76.2% were concerned about it. Interest in using doxy-PEP was independently associated with previous use of antibiotics for STI prevention (adjusted odds ratio, 3.09; 95% confidence interval, 1.78–5.35; P < 0.001), whereas those who were concerned about AMR were less interested in it (adjusted odds ratio, 0.51; 95% confidence interval, 0.36–0.72; P < 0.001). Conclusions Doxycycline postexposure prophylaxis was highly acceptable to gay and bisexual men and nonbinary people in Australia, and few factors distinguished between interest in using it or not. We recommend community and professional discussion and education about the effective use of doxy-PEP, AMR, and who would most benefit from doxy-PEP.