Abstract Background Unintended pregnancy predisposes women to unsafe abortion, malnutrition, mental illness, and even death. Though adolescent girls and young women are at higher risk of unintended pregnancy, there is a paucity of evidence in its burden and associated factors in sub-Saharan Africa. Therefore, this study aimed to assess the prevalence and factors associated with unintended pregnancy among adolescent girls and young women in sub-Saharan Africa. Method This study was a secondary data analysis of 36 sub-Saharan African countries with a total weighted sample of 17,797 adolescent girls and young women. A multilevel logistic regression model was fitted and, the Adjusted Odds Ratio (AOR) with a 95% Confidence Interval (CI) was reported to assess the association between the independent variables and unintended pregnancy in Sub-Saharan Africa. Result The pooled prevalence of unintended pregnancy in sub-Saharan Africa was 30.01 with 95% CI (29.38–30.74). In multivariable multilevel logistic regression analysis, adolescent girls, and young women with higher education (AOR = 0.71 95%CI 0.52–0.97), those who know modern contraceptive methods (AOR = 0.86 95%CI 0.75–0.98), and traditional contraceptive methods (AOR = 0.90, 95%CI 0.59–0.95), married (AOR = 0.80, 95%CI 0.73–0.88), those from female-headed households (AOR = 0.86,95%CI 0.78–0.94), had lower odds of unintended pregnancy. Whereas adolescent girls and young women from Central Africa (AOR = 2.09,95%CI 1.23–3.55), southern Africa (AOR = 5.23, 95%CI 2.71–10.09), and Eastern Africa (AOR = 1.07,95%CI 1.07–2.66) had higher odds of unintended pregnancy. Conclusion Prevalence of unintended pregnancy in Sub-Saharan Africa is high. Therefore, educating adolescent girls and young women, and improving their knowledge about family planning services is vital. It is also better for the government of countries in sub-Saharan Africa and other global and local stakeholders to work hard to ensure universal access to sexual and reproductive healthcare services, including family planning, education, and the integration of reproductive health into national strategies and programs to reduce unintended pregnancy.