The intricate relationship between immigration and health, a complex and multidimensional phenomenon, presents challenges for both receiving and sending countries of immigrants. Given the complex mechanisms involved, understanding and assessing the factors associated with disparities in immigrants’ health is a theoretical, methodological, and empirical challenge. Acknowledging and systematically understanding this phenomenon is crucial for the social cohesion of increasingly diverse countries. This introductory chapter reflects on the multifaceted nature of immigrant health, a theme that subsequent chapters in the book delve into from a more empirical perspective. This chapter first identifies current challenges in studies on immigrant health, offering reflections on these challenges’ effects on contemporary societies. Secondly, it provides an overview of immigration to Spain in recent decades, shedding light on the associated challenges in health policy management. Following this, the conceptual frameworks that guide most of the studies included in this book are presented. Special attention is given to the perspective of the healthy immigrant, discussing their ability to describe and explain phenomena related to immigrant health, along with the recognition of its limitations. The chapter concludes by presenting the main objectives of the book.