Integrated Water Resources Management (IWRM) represents a significant change from the older, separate ways of managing water resources. It encourages the coordinated planning and management of water, land and other related resources to improve social and economic conditions while also maintaining a healthy and sustainable environment. Nigeria has many water bodies and large river systems, but it still faces challenges in ensuring water security. These challenges include uneven distribution of water, seasonal changes, pollution, overuse and the effect of climate change. The objective of this chapter is to critically examine the principles, evolution, and implementation of Integrated Water Resources Management (IWRM) in Nigeria, assess its effectiveness in addressing water-related challenges, and propose strategic policy and research pathways for sustainable water governance aligned with national development goals and SDG 6. This chapter provides a comprehensive analysis of IWRM in Nigeria, exploring its conceptual foundations, relevance in addressing persistent water challenges such as uneven distribution, seasonal variability, pollution, and climate change impacts. It reviews national frameworks including the Water Resources Act (2004), National Water Policy, and the role of River Basin Development Authorities (RBDAs), highlighting gaps in coordination, stakeholder participation, and technical capacity. Using a desk-based synthesis of literature, policy documents, and institutional reports, it examines hydrological patterns, governance structures, and case studies from regions such as Hadejia-Jama’are, Benue River Basin, Lagos, and Cross River. Findings reveal that while IWRM offers opportunities for climate resilience, conflict mitigation, agricultural productivity, and urban water security, progress remains constrained by institutional fragmentation, inadequate funding, weak enforcement, and limited community engagement. Further studies should focus on (i) developing real-time water data systems and predictive models for climate variability; (ii) assessing socio-economic impacts of IWRM interventions; (iii) exploring innovative financing mechanisms and public-private partnerships; (iv) integrating indigenous knowledge into water governance; and (v) addressing emerging threats such as antimicrobial resistance in wastewater within IWRM frameworks. The chapter concludes with strategic recommendations for legal reforms, capacity building, innovative financing, and inclusive governance to strengthen IWRM implementation and achieve sustainable water management aligned with national development goals and SDG 6.