OBJECTIVES: To measure the usefulness of a Speaking Book (SB) as an educational tool for enhancing knowledge, understanding and recall of key vaccine-related information among caregivers in The Gambia, as well as its acceptability and relevance as a health promotion tool for caregivers and healthcare workers. DESIGN AND SETTING: We developed a multimedia educational tool, the vaccine Speaking Book, which contained prerecorded information about vaccines provided in The Gambia's Expanded Programme on Immunization. Using qualitative and quantitative methods, we then conducted a sequential study assessing the use of this tool among caregivers andhealthcare workers in The Gambia.Participants200 caregivers attending primary healthcare centres in The Gambia for routine immunisation services for their infants, and 15 healthcare workers employed to provide immunisation services at these clinics. OUTCOME MEASURES: We calculated the median knowledge scores on vaccine-related information obtained at baseline, 1-month and 3-month follow-up visits. Wilcoxon's matched-pairs signed-rank test was used to compare the difference in the median knowledge scores between baseline and 1-month, and between baseline and 3-month follow-up visits. RESULTS: Of the 113 caregivers who participated, 104 (92%) completed all three study visits, 108 (95.6%) completed the baseline and 1-month follow-up visits, and 107 (94.7%) completed the baseline and 3-month follow-up visits. The median knowledge score increased from 6.0 (IQR 5.0-7.0) at baseline to 11.0 (IQR 8.0-14.0) at 1-month visit (p<0.001), and 15.0 (IQR 10.0-20.0) at 3-month visit (p<0.001). Qualitative results showed high acceptability and enthusiasm for the Speaking Book among both caregivers and healthcare workers. The Speaking Book was widely shared in the community and this facilitated communication with healthcare workers at the primary healthcare centres. CONCLUSIONS: Context-specific and subject-specific Speaking Books are a useful communication and educational tool to increase caregiver vaccine knowledge in low/middle-income countries.