ObjectiveThe aim of this study was to assess the prevalence of not testing for HIV and its determinants among young adult women aged 15–29 years in Papua New Guinea (PNG).Design and settingThe study used secondary data from the 2016 to 2018 PNG Demographic and Health Survey (PNGDHS), a nationally representative cross-sectional survey that used a two-stage stratified sampling.ParticipantsA total weighed sample of 5164 young adult women aged 15–29 years were included in the analysis.Primary outcome measureEver been tested for HIV was the primary outcome of the study. All analyses were adjusted using survey weights to account for unequal sampling probabilities.ResultsThe prevalence of not testing for HIV was 58.8% (95% CI: 57.4% to 60.1%). The mean age was 21.65 years (SD = 4.23). Of the women who were not tested for HIV, the majority were never married (79.4%), without formal education (63%), not working (60.2%), and from rural areas (62.9%). In the multivariable analysis, those who were never married (adjusted OR (AOR) 4.9, 95% CI 3.6 to 6.6), had poor wealth index (AOR 1.8, 95% CI 1.3 to 2.5), were from rural areas (AOR 2.0, 95% CI 1.5 to 2.6), were from the Momase region (AOR 1.3, 95% CI 1.0 to 1.7), did not read newspapers or magazines (AOR 1.7, 95% CI 1.3 to 2.1), did not listen to the radio (AOR 1.5, 95% CI 1.1 to 2.0), experienced early sexual debut (AOR 1.5, 95% CI 1.1 to 1.9), had one sexual partner (AOR 1.5, 95% CI 1.2 to 2.0) and reported no sexually transmitted infection (STI) in the past 12 months (AOR 1.8, 95% CI 1.1 to 3.1) had higher odds of not testing for HIV.ConclusionsOur study found a very high unmet need for HIV testing among young adult women in PNG. Health promotion programmes should be designed to increase HIV knowledge and access to testing services, particularly targeting young women who are disadvantaged and from rural areas.