Background Reducing sexually transmitted infections among adolescents is an important public health goal in Australia and worldwide. This study estimated the association between condom use during last heterosexual sexual experience with two descriptive norms among a large, national sample of secondary school students from Australia. Methods A large, national online survey of 14- to 18-year-olds in Australia was conducted in 2018; a sub-analysis of sexually active participants (n = 2989) used multivariable logistic regression to estimate the relationships between condom use during last sexual experience and condom use norms. The analysis controlled for the effects of age, sex, sexual orientation, religious affiliation, remoteness and knowledge of sexually transmitted diseases. Results Overall, 1673 (56.0% [95% confidence interval: 54.2%, 57.8%]) sexually active respondents reported using condoms during their last sexual experience. Perceiving that all same-age peers used condoms conferred higher odds of using condoms during their last heterosexual sexual experience (adjusted odds ratio: 3.06 [95% CI: 1.6, 6.0]). Perceptions about whether the suggestion to initiate condom use came from boys, girls, or both boys and girls was not associated with condom use. Differences in condom use related to socio-demographic characteristics are reported. Conclusions As part of a holistic approach to sexuality education, health educators and service providers may emphasise that young people frequently choose to use condoms.