Infertility is perceived differently across socio-cultural contexts and studies have shown these perceptions affect the overall management of infertility. This study specifically explored the perceived causes of infertility among infertile married persons experiencing primary infertility in Kwara South, Nigeria. The study adopted a qualitative design. Infertile persons were recruited through snowball sampling technique. Data was collected through semi-structured in-depth interviews of 12 infertile married women and 7 infertile men. The data were analyzed using conventional content analysis with the aid of Atlas.ti 7. Findings showed that infertility is defined as barrenness and childlessness. Sociocultural factors rather than biomedical factors were exalted as primary causes of infertility. These include lifestyle choices or habits, rape, spiritual oppression, witchcraft/sorcery, trial and punishment from God. Understanding these perceptions will enhance the development of culture-specific programs targeted at managing infertility in Nigeria.