ASS1(argininosuccinate synthase 1) is a rate-limiting enzyme in the urea cycle, catalyzing the synthesis of argininosuccinate from citrulline and aspartate to ultimately produce arginine and support cellular metabolism. Increasing evidence suggests that ASS1 is commonly dysregulated in the tumor microenvironment, promoting tumor cell metastasis and infiltration. With a deeper understanding of tumor metabolic reprogramming in recent years, the impact of ASS1 dysregulation on abnormal tumor metabolism has attracted growing interest among researchers. In tumors with lacked or downregulated expression of ASS1, tumor cells become 'addicted' to exogenous arginine. Several strategies for arginine deprivation have been developed and entered clinical trials for treating such tumors. Therefore, we focus on elucidating the commonalities and characteristics of ASS1 dysregulation in tumors, as well as its implications for diagnosis, treatment, and prognosis. The mechanisms by which ASS1 gene dysregulation leads to metabolic abnormalities in tumor cells vary across different types of tumors. Extensive experimental studies have demonstrated that overexpression or low expression of ASS1 exhibits varying effects-either inhibitory or stimulatory proliferation-on tumor cells across different types. Restoring its expression can inhibit proliferation in some tumors lacking or downregulating ASS1 but can promote metastasis and infiltration in others (e.g., resistance to arginine deprivation therapy). Additionally, the expression level of ASS1 dynamically changes during tumorigenesis and progression. Finally, this review discusses the diagnostic, therapeutic, and prognostic value of ASS1 in future clinical practice.