Food insecurity and malnutrition are global challenges and might escalate with the effect of climate change. Whilst transitioning from subsistence to commercial agriculture is seen as a promising strategy to address these issues, the specific pathways remain unclear. This is in light of literature showing mixed effects of crop commercialisation on food security and nutrition (FSN). We use data from a household survey of 388 households conducted in Nyandarua – one of Kenya's leading potato‐producing counties but faces higher levels of malnutrition compared to the national average. In the study, FSN was measured using the food insecurity experience scale (FIES) and the households' dietary diversity score (HDDS). The effect of crop commercialisation on the two FSN indicators was measured using the ordered probit and truncated Poisson regression models. The results show a moderate level of potato commercialisation. The results indicate a moderate level of potato commercialisation (based on a commercialisation score of 0.4 out of a possible 1). Whilst most households were generally food secure (96%), dietary diversity was somewhat limited. The Econometric analysis reveals that, whilst potato commercialisation did not influence food security, it has a positive effect on household dietary diversity. This study contributes to the understanding of the pathways through which the commercialisation of staple food crops impacts FSN – a contribution that has received limited research attention in the literature. Additionally, the study also emphasises the importance of considering local contexts and preferences when designing interventions to improve FSN outcomes. Based on the findings, we reflect on the implications of the findings in nutrition‐specific and responsive initiatives in a developing country context.