Background Young adults, aged 18–30 years, comprise the largest proportion of sexually transmissible infection (STI) notifications in Australia compared with other age groups. Understanding the influence of partner and friendship networks on their STI testing practices may enhance health promotion efforts to increase testing for this group. Method: Participants aged 21–30 years, living in Australia for ≥3 years, were recruited within nightlife precincts in Melbourne, Australia. They completed a survey on demographic items, sexual health attitudes, sexual health knowledge and STI testing experiences and perceptions. Responses to items related to talking to partners and friends about STI testing were allocated partner and friend communication scores. Analyses included χ2 tests of independence and independent sample t-tests. Results: Overall, 36.5% (61/167) of participants had tested for STIs in the previous 12 months. Of those who had tested for STIs, most had significantly higher numbers of sexual partners in the same period (P < 0.05), and were significantly more likely to have felt at risk of STI acquisition (P < 0.05). Significantly greater mean partner and friend communication scores were associated with higher numbers of sexual partners, feeling at risk of STIs, and testing for STIs in the previous 12 months (all P < 0.05). There were no significant differences when participants were stratified by gender or age. Conclusion: Talking to partners and friends about STI testing is associated with testing rates for young adults. Feeling at risk and increased numbers of sexual partners may be associated with the promotion of STI testing among friends and partners.