Objectives: This thesis describes a study that designed, implemented and assessed the effect of a food hygiene intervention on mothers’ food hygiene practices as primary outcomes, and the impact of the interventions on the level of microbiological contamination in food as a secondary outcome. An additional objective was to explore whether food hygiene interventions can be integrated into nutrition, health and water, sanitation and hygiene (WASH) strategies and programmes in Nepal. Methods: The theoretical and practical approach of Behaviour Centred Designed was employed. In step-A: Assess, a systematic literature review was conducted to identify sectoral knowledge and programmatic gaps on food hygiene and sectoral policy documents analysis was done as part of gray literature review to ascertain whether food hygiene interventions can be integrated into Nepal’s health, WASH and nutrition programming. In step-B: Build, formative research was carried out to identify and prioritise key food hygiene behaviours, and inform the intervention design. In step-C: Create, a scalable food hygiene intervention package was designed and tested using a novel approach to behaviour change employing emotional drivers and changing behaviour settings. In Step-D, the intervention was Delivered by female food hygiene motivators in four intervention clusters over a period of three months while four clusters acted as a control group in a rural area of Nepal. In Step E: Evaluate, a Cluster Randomized, Before-After study with Control (BAC) was employed. Behavioural outcomes were measured before and after the intervention in 239 households with a child aged 6-59 months in four intervention and four control clusters. The microbiological contamination in commonly-used child foods was measured in a sub-sample of 80 households. Results: Systematic review identified the need for research into improving food hygiene behaviour to reduce contamination in food and improve health outcomes in low-income settings. Nepal’s policy environment can enable the integration of food hygiene promotion within ongoing WASH, nutrition and health programmes. Five key food hygiene risk behaviours were prioritized, and likely determinants of behaviour change were identified through formative research. The motivational and creative food hygiene intervention package was designed and delivered in community settings. The intervention was effective in significantly improving multiple food hygiene behaviours. The 5 targeted food hygiene 4 behaviours were rare at baseline. Forty five days after the 3 months intervention, key behaviours were more common in the intervention group than in the control group (43% [SD14] vs. 2% [SD 2], p=0.02). The difference of differences was an increase in mean proportion of 42% (p=0.02). The intervention appeared to be equally effective in improving all five behaviours and in all intervention clusters. Commonly-used child foods from the intervention and control clusters were heavily contaminated with total coliforms and E. coli during child feeding at baseline and the behavioural intervention was effective in significantly reducing the contamination in the intervention group during follow-up. After adjusting for baseline, the intervention reduces the mean coliform count by -2.00 log10 cfu/gm (p=0.020) and E. coli by -1.00 log10 cfu/gm (p=0.083). Contamination in water was low as compared to food at baseline and did not improve after the intervention.. Conclusion: This systematic approach employing emotional drivers and change in behavioural settings substantially altered multiple food hygiene behaviours and reduced microbial contamination in commonly-used child food in Nepal. Ingestion of microbes by children can only be eliminated if the food hygiene intervention deals with all key behaviours. This study responds to an important evidence gap. Current evidence, to which this study has contributed , is sufficient to merit prioritisation of food hygiene by those concerned with designing more effective WASH, health and nutrition programmes. The work suggests that interventions on food hygiene should have a higher priority than those on water treatment, which is not currently the case in development projects. The BCD approach provided a theory of change and a useful process framework for the design, delivery and evaluation of the intervention. Additional research is needed to test the impact of such interventions on both behaviour and health outcomes. Further tests would help to determine if the intervention can be replicated in diverse settings and at large scale and so add value to existing programmatic responses to poor WASH and undernutrition. The implementation of a tested food hygiene package through a scalable pilot was identified as a next step towards demonstrating the delivery of hygiene interventions through existing service delivery mechanisms in Nepal.