Nowadays, brand personality is one of the most studied concepts regarding the brand-consumer relationship. However, the antecedents of this concept have received little interest from researchers. Our empirical investigation, applied to a sample of 309 Tunisian customers of three mobile telephony operators, shows that the perception of a brand personality depends on the level of self-congruence with some components of brand image. Functional congruence that assesses the matching between utilitarian performances of products and customers’ needs is also shown to influence brand personality. The results of our research also confirm that self-image congruence has a significant effect on functional congruence. In theoretical terms, this work contributes in a better understanding of the way brand personality (and so brand image) is formed in the spirit of a customer. It also confirms that brand personality, self-image congruence and functional congruence play a significant role in enhancing brand loyalty. The extracted results also present to marketing managers in the mobile telephony sector and in other sectors, precise recommendations for the implementation of sound and successful brand, differentiation and communication strategies.