Code-switching, the practice of alternating between two or more languages within a conversation or discourse, is a defining feature of multilingual societies. This study examines the influence of code-switching on English grammar, focusing on how structural, syntactic, and lexical elements are shaped through continuous language contact. In multilingual contexts, speakers often blend linguistic systems to achieve communicative efficiency, cultural expression, and social identity. Such interactions lead to the emergence of hybrid grammatical patterns, including shifts in word order, omission or adaptation of function words, and the borrowing of morphological features. While traditional linguistic perspectives often regard these variations as deviations from standard grammar, contemporary approaches recognize them as systematic and rule-governed phenomena. The paper explores how code-switching contributes to the evolution of English by incorporating features from regional and indigenous languages, thereby enriching its expressive capacity. It also highlights the pedagogical implications for English language teaching, suggesting that awareness of code-switching can help educators address learner errors more effectively and adopt inclusive teaching strategies. Furthermore, the study underscores the role of socio-cultural factors such as identity, power dynamics, and globalization in shaping linguistic practices. By analyzing real-life examples from multilingual communities, the research argues that code-switching should not be viewed merely as linguistic interference but as a dynamic resource that reflects linguistic creativity and adaptability. Ultimately, the paper advocates for a descriptive rather than prescriptive approach to understanding English grammar in multilingual settings.