Secreted phosphoprotein 1 (SPP1), also known as osteopontin, is a multifunctional glycoprotein that plays a critical role in various physiological processes, including cell adhesion, chemotaxis, immune regulation, and tissue remodeling. Originally identified as a key component of the bone matrix, SPP1 is now recognized for its broad involvement in numerous tissues and significant impact on both normal physiology and disease progression. Dysregulation of SPP1 has been strongly implicated in the pathogenesis and progression of several diseases, including cancer, cardiovascular diseases, autoimmune disorders, and chronic inflammatory conditions. The expression of SPP1 is tightly regulated by genetic and nongenetic mechanisms. Genetic alterations, such as single-nucleotide polymorphisms, insertions and deletions, and structural variations within the SPP1 gene, have been associated with increased susceptibility to various diseases, influencing disease severity and outcomes. Additionally, nongenetic regulations, including DNA methylation, histone modifications, and long noncoding RNAs, play crucial roles in modulating SPP1 expression in response to environmental and cellular signals. This review provides a comprehensive overview of the genetic and nongenetic regulatory mechanisms governing SPP1 and examines their implications in disease pathogenesis. By integrating recent findings, this review highlights the complex interplay between genetic predispositions and nongenetic regulations in determining SPP1 activity and offers new insights into its role as a potential biomarker and therapeutic target. Understanding these regulatory pathways is essential for the development of targeted interventions for diseases in which SPP1 plays a pivotal role.