<p>Cancer and inflammatory diseases are critically influenced by dynamic interactions between pathological tissues and the host immune system. The precise migration of immune cells into the local microenvironments of tumors or inflammation is a fundamental prerequisite for them to exert their functions. Immune reservoirs, including tertiary lymphoid structures, secondary lymphoid structures, bone marrow and the intestinal tract, serve as critical mobilization hubs for diverse lymphoid and myeloid populations to infiltrate tumors or inflamed sites. The directional migration of immune cells is orchestrated through complex regulatory networks involving chemokine or cytokine-receptor pairs, adhesion molecule interactions, extracellular vesicle signaling, metabolic reprogramming and microbiota modulation. In both tumors and inflammation, immune cell trafficking shapes the local immune landscape, contributing to either immune protection or pathological progression. Contemporary therapeutic strategies targeting immune cell migration encompass the following axes: precision modulation of chemokine or cytokine networks, architectural reprogramming of lymphatic structures or extracellular matrix, dietary intervention and strategic manipulation of microbiome. Nevertheless, clinical translation remains hindered by microenvironmental heterogeneity, suboptimal migratory efficiency, and technical limitations in longitudinal tracking of cellular dynamics. This review integrates recent findings from oncology and inflammatory diseases to explore the origins, phenotypes and trafficking mechanisms of migratory immune cells, highlighting how advances in understanding immune migration across cancer and inflammation can inform therapeutic innovation and precision immunomodulation.</p>