For decades, countries throughout the world have failed to meet sanitation-related development goals. Access to safe sanitation is undeniably linked to improved health outcomes; yet, 2.4 billion people, globally, still lack access. The persistent failure to meet sanitation goals suggests that our understanding of the factors that influence sustainable sanitation access and utilisation is incomplete. Despite growing availability of toilets in informal settlements, there is evidence that women, in particular, may adopt other strategies for managing their sanitation needs. Empirical data documenting the motivations underlying such practices in sub-Saharan Africa are limited. This study uses cross-sectional data collected in 2016 from women in Mathare Valley Informal Settlement in Nairobi, Kenya. Boosted and logistic regressions were used to investigate which factors were associated with women's common sanitation patterns. Lack of privacy and insecurity at toilets and neighbourhood disorganisation emerged as important factors - particularly for women who reported regularly using buckets or plastic bags for urination/defecation. These findings suggest that availability of toilets may not be enough to eliminate sanitation-related health risks in informal settlements. Future interventions may need to address other barriers to sanitation access if sustainable gains in this important public health area are to be achieved.