AbstractA study tested an extended Theory of Planned Behaviour (TPB) model, inclusive of measures of ethnical identification and perceived ethnic group norms, in the ethnical food purchasing domain. One hundred and thirty‐five Jamaicans, living in the Brixton neighbourhood, London, were administered a self‐reported questionnaire measuring the classical TPB components (attitudes, subjective norms, perceived behavioural control, behavioural intentions) plus three additional components: identification with the Jamaican group, perceived norms of the Jamaican group and past behaviour. Results of hierarchical multiple regressions showed that past behaviour, ethnical identification and perceived group norms explain an additional proportion of variance in intentions, independently of attitudes, subjective norms and perceived control. A two‐way interaction, between ethnical identification and perceived group norms, was detected. A stronger relation between group norms and intentions emerged among high ethnical identifiers. Theoretical and practical implications are discussed. Copyright © 2008 John Wiley & Sons, Ltd.