Background There has been increasing attention on assessing rates of sexting in adolescents and of the potential negative effects of the behaviour. Our aim was to assess rates and correlates of sexting in Australian students in years10, 11 and 12. Methods: The current study was part of The Fifth National Survey of Australian Secondary Students and Sexual Health and reports on responses of 2114 students (811 male, 1303 female). Sexting was assessed using six items: sending a sexually explicit written text message; receiving a sexually explicit text message; sending a sexually explicit nude or nearly nude photo or video of themselves; sending a sexually explicit nude or nearly nude photo or video of someone else; receiving a sexually explicit nude or nearly nude photo or video of someone else; and using a social media site for sexual reasons. Results: Approximately half of the students had received (54%, 1139/2097) or sent (43%, 904/2107) a sexually explicit written text message. Sexually explicit images had been received by 42% (880/2098) of students, one in four students had sent a sexually explicit image of themselves (26%, 545/2102) and one in 10 had sent a sexually explicit image of someone else (9%, 180/2095). Finally, 22% (454/2103) of students had used social media for sexual reasons. Sexting was associated with several correlates. Conclusions: Sexting was relatively common in this sample of year 10, 11 and 12 Australian students, particularly among older students, those who are sexually active, and those who use recreational substances.