Background <p>The nonuse of modern contraceptives among sexually active Adolescent Girls and Young Women (AGYW) impacts their health, future aspirations, and overall well-being. Addressing nonuse is crucial in empowering AGYW to take control of their future. This study aimed to determine the proportion of sexually active AGYW who are not using modern contraceptives and the associated factors in selected districts of the Busoga subregion, Eastern Uganda.</p> Methods <p>The study used a cross-sectional design utilizing quantitative data from 490 randomly selected sexually active young people in the Busoga subregion. Data were collected through in-person interviews using a questionnaire designed using Kobo Collect software. A multivariable modified Poisson regression model was used to estimate prevalence ratios for the factors associated with the non-utilization of modern contraceptives.</p> Results <p>The mean age of respondents was 19.3 years (Standard Deviation = 6.7). Out of 490 sexually active adolescent girls and young women, 43.1% were not using modern contraceptives. The prevalence of non utilization of modern contraceptives was 33% higher among adolescent girls and young women who are not confident discussing contraceptives with peers and older Adults (APR = 1.331 95% CI:1.056–1.667) compared to those who were confident. Likewise, adolescent girls and young women who were not confident discussing about contraceptives with their partners had a 37% higher prevalence of non-utilization (APR = 1.373; 95% CI: 1.023–1.845) and those who found modern contraceptive service points inaccessible had a 38% higher prevalence of non-utilization (APR = 1.386; 95%CI: 1.021–1.845). On the other hand, the prevalence of non-utilization of modern contraceptives was 37% lower among marrieds (APR = 0.631; 95% CI:0.475–0.838) compared to singles, while the prevalence of non-utilization is 38% lower among those who interact with community health workers/Village Health Teams (APR = 0.623; 95%CI: 0.401–0.967) compared to their counterparts.</p> Conclusions <p>The nonuse of modern contraceptives among Adolescent girls and young women is high in eastern Uganda. Nonuse is influenced by sociodemographic factors and social norms. Interventions should enhance confidence building in discussing contraceptives through peer-led programs, make modern contraceptives more accessible, strengthen community-based outreaches and target young married people with tailored family planning awareness emphasizing the role of contraception.</p>