Owing to nutritional transition in Cameroon, one in two adults is overweight and one in five is obese, and 8·1 % of children are overweight and 2·1 % are obese. Given this phenomenon, dietary intake assessment is needed to establish appropriate preventive nutrition-sensitive strategies. Our aim was to develop and test the validity of two food portion photograph books (FPPB) to be used as visual aids for adults and children taking part in a 24-h dietary recall. To design FPPB, interviews and focus group discussions were undertaken with women to obtain consensus on the local categorisation of foods. For each cooked and weighed food, three photographs of the average small, medium and large serving portion sizes were taken, and four intermediary portion sizes were calculated. To validate the FPPB, a sample of adults (361) and children (224) were asked, at meal times, to self-serve a food portion prepared in the household and the portion sizes were weighed; 24 h after the measurement, the same subjects were shown the appropriate FPPB and were asked to indicate the food and the portion they consumed. In adults, of the 821 portions tested, 77 % were accurately estimated, whereas in children 74 % of the 556 portions tested were accurately estimated. For both groups, the small- and medium-sized portions were frequently selected and accurately estimated (>70 %). Our findings suggest that the adult and children’s FPPB can be used in Cameroon to estimate food portion sizes, and thus nutritional intake in the frame of the 24-h dietary recall.