This paper adds to the debate about factors influencing consumer behaviours that lead to the actual purchase of organic food in both developed and developing countries. Accordingly, authors seek to understand how consumers’ knowledge about organic food and consumers’ overall health consciousness play out as mechanisms for consumers’ behaviours leading to actual purchase. Samples from Tanzania as a developing country and Denmark as a developed country are used. A total of 1393 consumers filled the questionnaire. The study found that consumer knowledge and health consciousness function as underlying mechanisms in the relationship of attitude and subjective norms for actual purchase of organic food behaviour in Tanzania. In addition, consumer knowledge and health consciousness function as an underlying mechanism in the relationship of attitude and perceived behaviour control for actual purchase of organic food in Denmark. The study argues for enhancing consumers’ knowledge of organic food as the latter has been championed for its perceived health benefits in both developed and less developed countries.