Background: In Northern Nigeria, short birth interval is common. The word kunika in the Hausa language describes a woman becoming pregnant before weaning her last child. A sizeable literature confirms an association between short birth interval and adverse perinatal and maternal health outcomes. Yet there are few reported studies about how people view short birth interval and its consequences. In support of culturally safe child spacing in Bauchi State, in North East Nigeria, we explored local perspectives about kunika and its consequences. Methods: A qualitative descriptive study included 12 gender-segregated focus groups facilitated by local men and women in six communities from the Toro Local Government Area in Bauchi State. Facilitators conducted the groups in the Hausa language and translated the reports of the discussions into English. After an inductive thematic analysis, the local research team reviewed and agreed the themes in a member-checking exercise. Results: Some 49 women and 48 men participated in the 12 focus groups, with an average of eight people in each group. All participants were married with ages ranging from 15 to 45 years. They explained their understanding of kunika, often in terms of pregnancy while breastfeeding. They described many disadvantages of kunika, including health complications for the mother and children, economic consequences, and adverse impact on men's health and family dynamics. The groups concluded that some people still practise kunika, either intentionally (for example, in order to increase family size or because of competition between co-wives) or unintentionally (for example, because of frequent unprotected sex), and explained the roles of men and women in this.