Background <p>Condom use is an essential component of strategies to improve the sexual and reproductive health of adolescents and young adults (AYA). However, it remains a challenge for many Sub-Saharan African countries, including Liberia. This study aimed to examine the effects of individual and contextual factors on condomless sex within the past 12 months among AYA in Liberia.</p> Methods <p>A secondary analysis was conducted using data from the 2019-2020 Liberia Demographic and Health Survey (2019-20 LDHS). Sexually active AYA were included in the study. A simultaneous assessment of the effects of individual and community characteristics on unprotected sex was conducted using a multilevel mixed-effects logistic regression model. The adjusted odds ratios (aORs) and their 95% confidence intervals (CIs) for condomless sex were estimated.</p> Results <p>Of the 2,260 AYA included in the analysis, 68.3% were female, and 40.0% were living in poor households. Their mean age (± SD) was 19.3 (±2.6) years. Only 31.6% reported a history of HIV testing. The prevalence of condomless sex was 83.1%. Individual and contextual factors explained 71.4% of the variation in condomless sex among AYA. In the multivariable analysis, condomless sex was less likely among males (aOR = 0.36 [0.27–0.47]), those with moderate (aOR = 0.67 [0.48–0.94]) or high (aOR = 0.46 [0.31–0.67]) media exposure, and those with occasional partners (aOR = 0.61 [0.39–0.96]). Having a professional activity was associated with higher odds (aOR = 1.52 [1.17–1.97]). Contextual factors associated with lower odds included high community-level education (aOR = 0.65 [0.43–0.98]), urban residence (aOR = 0.54 [0.37–0.78]), and living in South-Eastern B region (aOR = 0.52 [0.3–0.93]; reference = North-Western).</p> Conclusion <p>The study shows a high prevalence of condomless sex in Liberia. Condom promotion strategies must take into account individual and contextual factors such as gender and regional inequalities.</p>