Malaria vaccine is a potentially effective addition to the armamentarium for malaria control. The candidate RTS,S malaria vaccine has undergone phase III clinical trials and WHO has indicated that a policy recommendation is possible in 2015. Given the delays with adoption of other novel interventions including vaccines, there is a need to ensure that all elements that will inform the decision to adopt a malaria vaccine, including community willingness, will be available on time. This study was carried out to assess the willingness of caregivers of under-5 children to accept a malaria vaccine once available and recommended for use. 427 consenting caregivers, selected using a cluster sampling technique, from five communities in Ibadan, Nigeria, participated in a questionnaire. In-depth interviews (IDIs) were conducted among 47 key community members. Data were analysed using descriptive statistics, Chi-square and logistic regression at p≤0.05. Thematic content analysis was used to analyse the transcribed IDI data. The mean age of survey respondents was 29.8±5.8 years. Only 20.1% of the respondents had ever heard of malaria vaccine; 87.0% showed willingness to accept a malaria vaccine. Reasons stated for not willing included 'husband did not want immunisation' (73.6%), 'felt it might be expensive' (47.2%) and 'felt it might paralyse children' (24.5%). Nearly half (48.7%) of the respondents said that if vaccine is not given orally like polio vaccine it might not be accepted. Influence of community health workers was found to predict willingness to accept a malaria vaccine (OR: 0.316, 95% CI: 0.142-0.705). IDI participants were favourably disposed to introduction of a vaccine against malaria, although they had concerns about the formulation of the vaccine and possible adverse events. Well-designed communication strategies implemented prior to the introduction of a malaria vaccine would be essential to foster a supportive environment for eventual adoption and acceptance thereof.