This chapter examines the practical integration of generative artificial intelligence (GenAI) in TESOL, focusing on its pedagogical applications across listening, reading, speaking, writing, and intercultural communication. Grounded in established second language acquisition theories, the chapter illustrates how GenAI can support adaptive input, scaffolded interaction, meaningful output, and authentic communicative tasks. Drawing on empirical studies and classroom-based examples, it demonstrates how GenAI enables personalised learning pathways, real-time feedback, low-anxiety practice environments, and differentiated instruction for learners across age groups and proficiency levels. The chapter also highlights GenAI’s role in supporting diverse pedagogical approaches, such as communicative language teaching, experiential learning, flipped classrooms, and collaborative learning. At the same time, it critically addresses key challenges, including algorithmic bias, cultural misalignment, over-reliance on automated feedback, data privacy, and unequal access to AI technologies. The analysis emphasises the central role of teacher mediation, instructional design, and AI literacy in ensuring that GenAI enhances rather than constrains language learning. Overall, the chapter positions GenAI as a powerful pedagogical resource whose effectiveness depends on ethical, context-sensitive, and theory-informed implementation.