As a pervasive environmental hazard, air pollution has been reported to exert profound adverse effects on the brain through multiple toxicological pathways. This chapter aims to provide a comprehensive introduction of how air pollutants such as fine particulate matter (PM2.5), ozone, or nitrogen oxides (NOx) initiate a cascade of biological responses that compromise neural function, ultimately contributing to the occurrence and development of neurological diseases. Specifically, seven core toxicological mechanisms, including inflammatory response, oxidative stress, activation of the autonomic nervous system, DNA damage and repair, hypothalamic–pituitary–adrenal (HPA) axis activation, alteration of host microbiome, and epigenetic modifications are delineated. Noticeably, these mechanisms may interact with each other, resulting in increased vulnerability to neurological disorders caused by air pollution. In addition, several key molecular signaling pathways such as mitogen-activated protein kinase (MAPK), Nrf2-antioxidant responsive element (ARE), NOD-like receptor family pyrin domain containing 3 (NLRP3), and Janus kinase-signal transducer and transcription activator (JAK/STAT) signaling pathways as well as the role of gut–brain axis are discussed in detail. This mechanistic insight is intended to inform future research directions and provide a fundamental basis for evidence-driven policy and public health interventions aimed at mitigating the health burden of air pollution.