Few studies investigate sexual health among Chinese international students in Australia. We recruited domestic (n = 623) and Chinese international (n = 500) students for separate online surveys on sexual behaviours and knowledge. Samples were compared using Chi square, Fisher’s exact and equality of medians tests. Domestic students were more likely than international students to have ever touched a partner’s genitals (81% vs. 53%, p < 0.01), had oral sex (76% vs. 44%, p < 0.01), vaginal intercourse (67% vs. 41%, p < 0.01) and anal intercourse (31% vs. 6%, p < 0.01). Domestic students were younger when they first touched a partner’s genitals (16 vs. 18 years, p < 0.01), had oral sex (17 vs. 18 years, p < 0.01) and vaginal intercourse (17 vs. 18 years, p < 0.01). Domestic students were less likely than Chinese international students to report only one lifetime partner for touching genitals (22% vs. 50%, p < 0.01), oral sex (25% vs. 55%, p < 0.01), vaginal intercourse (30% vs. 58%, p < 0.01) and anal intercourse (54% vs. 88%, p < 0.01). Domestic students were more likely than Chinese international students to use the oral contraceptive pill (48% vs. 16%, p < 0.01) and long-acting reversible contraceptives (19% vs. 1%, p < 0.01). Domestic students scored higher than international students on a contraception and chlamydia quiz (4/5 vs. 2/5, p < 0.01). Domestic and Chinese international students differed in sexual behaviours and knowledge highlighting the need for relevant sexual health promotion for both groups.