The use of English in advertising across non-English-speaking countries is pervasive, often seen as a strategy to evoke prestige, modernity, and global appeal. However, its effectiveness may depend on factors such as text length, linguistic complexity, and local language use, which remain underexplored. This study investigates how Spanish and Polish consumers respond to English-language advertisements of varying lengths (for a cream, a watch, and a perfume) featured in women’s glossy magazines, examining whether English is as effective as often assumed or if its impact is moderated by these factors. The study involved 210 university students: 105 from the Catholic University of Murcia (Spain) and 105 from Maria Curie-Skłodowska University (Poland). Findings reveal that while both Spanish and Polish participants generally favored advertisements primarily or partially in English (i.e., code-mixed) over those solely in their native languages, this preference did not consistently enhance their evaluations of the advertised products. Products were rated more favorably when presented in the native language, especially in longer, more linguistically complex ads. By contrast, shorter ads elicited more positive attitudes towards the product when English was used. These findings suggest that the symbolic appeal of English interacts with linguistic complexity and cultural factors, indicating that English is not universally effective in advertising. While English remains attractive to consumers, its use should be balanced with considerations of clarity, comprehension, and the cultural resonance of the local language to avoid undermining advertising effectiveness. Results highlight the nuanced role of English in advertising, challenging assumptions about its universal appeal and providing insights into designing multilingual campaigns that resonate with diverse audiences across Europe.