Branding sustainability across borders: The role of extension fit, environmental concern, and brand image in Portugal and Turkey

This study explains how consumers form attitudes toward sustainable fashion line extensions by integrating Brand Extension Theory (BET) with the Theory of Planned Behavior (TPB). Using survey data from 786 consumers in Portugal and Turkey, with H BEF itself positively predicts AT and transmits part of EC's and BI's effects. The model explains R2 ≈ 0.742 of BEF and R2 ≈ 0.476 of AT, supporting the explanatory adequacy of the integrated framework. A multi-group analysis suggests context-sensitive differences between Portugal and Turkey, which we interpret in light of policy-normalization (Portugal) versus crisis-salience (Turkey); given partial measurement invariance, these contrasts are framed as cautious tendencies. Overall, findings underscore fit as the mechanism through which consumers synthesize values and brand heuristics, clarifying why strong brand image alone does not guarantee perceived sustainability congruence in fast-fashion contexts.