This article examines the influence of framing a brand's concept as functional versus symbolic in the advertising of a new vertical line extension. In this research, we carried out two online experiments and collected data from 415 participants recruited from MTurk to investigate the moderating role of believability on the effect of brand concept framing on consumers' purchase intentions of vertical line extensions. The results indicate that (i) consumers evaluate a vertical extension advertising message more positively when it is framed in a consistent manner with the targeted price/quality segment and not with its parent brand or existing product line and that (ii) this effect is moderated by consumer believability such that an advertising framing effect is found for high, but not low, in believability. Perceptions of category fit mediate the relationship between framing brand concept and the evaluation of the extension. This study contributes to the advertising and marketing literature by exploring how consumers can interpret brand concept framing in advertising messages of vertical line extensions differently depending on their level of believability and, in turn, influence their purchase intentions.