This article investigates 90 Shanghainese participants' cross-generational use and knowledge of 140 English loanwords in Shanghainese which are deemed as an important part of Shanghai Regional Culture (SRC). The quantitative results reveal that the older participants use and know much more of English loanwords than the younger ones, and that many distinctive loan verbs and nouns are replaced by Putonghua (PTH) equivalents. By analysing the results of both the questionnaire survey and interviews based on the Guy's [1990. "The Sociolinguistic Types of Language Change." "Diachronica" 7: 47-67] classificatory paradigm of language changes, I argue that this lexical replacement, as a type of 'imposition', caused by the intense contact between Shanghainese and PTH, suggests lexical attrition of Shanghainese, which leads to linguistic convergence and cultural homogeneity. In the new contact triggered by nationwide migration, the national lingua franca has cut off the direct contact between Shanghainese and English. Shanghainese has retreated from a regional koiné to a vernacular.