This article assesses the effectiveness of The Great WASH Yatra handwashing awareness raising campaign in India on changing visitors' intention to wash hands with soap after using the toilet and the underlying behavioural determinants. Interviews based on the RANAS (Risk, Attitudes, Norms, Abilities, Self-regulation) model of behaviour change were conducted with 687 visitors before and after their visit to the campaign. Data showed that a campaign visit had little effect on the intention to wash hands with soap, even when comparing visitors who had actively participated in handwashing games with those who had not. After a campaign visit, knowledge about the benefits of washing hands had increased by almost half a standard deviation. A multiple linear regression analysis revealed that when considering all behavioural determinants change scores simultaneously, they were able to explain 57% of the variance in the intention change score. These findings suggest that substantively changing behaviour requires more than improving knowledge and emphasizing the importance of washing hands. Identifying the crucial behavioural determinants for handwashing may be an important first step in planning effective large-scale promotion programmes.