Falsified medicines are pharmaceutical products purposefully and unlawfully produced or mislabelled in terms of identity and source to appear genuine to unsuspecting victims. They pose a significant public health risk in Africa. In Nigeria, falsified medicines have negatively affected the reliability of the health sector. They cause incurable diseases, illness, and even death for consumers. Evidence regarding the contributing factors to the prevalence of falsified medicines in Nigeria is diverse and inconclusive. This study seeks to find out the contributing factors to the prevalence of falsified medicines in Nigeria. Interpretivism, induction and exploration were the research methodology that guided the study. Qualitative research method was adopted for data collection and analysis to elicit context and data rich information from the qualitative data. Eight public health professionals were recruited through purposive sampling from five regulatory/health institutions in Nigeria. Nineteen sub-themes further distilled into four overriding themes emerged to address the research questions, namely: systemic challenges; multidimensional risks; inadequate and weak measures; and systemic change. The study corroborates a significant body of the literature which identifies factors causing the prevalence of falsified medicines in Nigeria. It also validates existing research which identifies public health risks, industry health risks, economic health risks and government revenue risks as direct and tangential impacts of falsified medicines on public health. It finds that the current measures are weak and inadequate and recommends solutions which can engender systemic change in the pharmaceutical ecosystem in Nigeria. These include overhauling of the existing regulatory and enforcement mechanisms; entrenching good politics, socio-economic improvement of the conditions of Nigerians; and effective monitoring and surveillance of the pharmaceutical supply chain. These contributions add to existing knowledge and the literature and identifies the need for the Nigerian government to show more leadership, improve the welfare of majority of Nigerians who are poor, and deploy subsidies and interventions (such as health insurance scheme) to make more access available to poor Nigerians to get quality, safe and affordable drugs which can treat their health conditions and enhance their well-being.