(1) Background: Improving sexual autonomy among women in sexual unions comes with various benefits, including the reduction of sexually transmitted and blood-borne infections. We examined the relationship between mass media exposure and safer sex negotiation among women in sub-Saharan Africa (SSA). (2) Methods: The study involved a cross-sectional analysis of Demographic and Health Survey (DHS) data of 29 sub-Saharan African countries. A total of 224,647 women aged 15-49 were included in our analyses. We examined the association between mass media exposure and safer sex negotiation using binary logistic regression analysis. The results are presented using a crude odds ratio (cOR) and adjusted odds ratio (aOR), with their respective confidence intervals (CIs). Statistical significance was set at p < 0.05. (3) Results: The overall prevalence of safer sex negotiation among women in sexual unions in SSA was 71.6% (71.4-71.8). Women exposed to mass media had higher odds of negotiating for safer sex compared with those who had no exposure (aOR = 1.94; 95% CI = 1.86-2.02), and this persisted after controlling for covariates (maternal age, wealth index, maternal educational level, partner's age, partner's educational level, sex of household head, religion, place of residence, and marital status) (aOR = 1.40; 95% CI = 1.35-1.46). The disaggregated results showed higher odds of safer sex negotiation among women exposed to mass media in all the individual countries, except Ghana, Comoros, Rwanda, and Namibia. (4) Conclusions: The findings could inform policies (e.g., transformative mass media educational seminars) and interventions (e.g., face-to-face counselling; small group sensitization sessions) in SSA on the crucial role of mass media in increasing safer sex practice among women in sexual unions. To accelerate progress towards the achievement of the Sustainable Development Goal five's targets on empowering all women and safeguarding their reproductive rights, the study recommends that countries such as Ghana, Comoros, Rwanda, and Namibia need to intensify their efforts (e.g., regular sensitization campaigns) in increasing safer sex negotiation among women to counter power imbalances in sexual behaviour.