Objectives: This study was conducted to measure financial toxicity (FT) among patients with cancer in Vietnam using the COmprehensive Score for financial Toxicity (COST) and to describe the cost management strategies employed by these patients. Methods: This comprehensive cross-sectional study enrolled 634 patients from 2 specialized oncology hospitals in Vietnam. Using COST cut-off scores, FT was classified as none/mild (≥26), moderate (14-25), or severe (≤13). Cost management strategies, or coping mechanisms, were classified into 4 groups: lifestyle changes, financial resource strategies, treatment modifications, and support seeking. Results: The prevalence of FT was 91.8%, with 51.7% of participants demonstrating severe and 40.1% exhibiting moderate FT. Severe FT was significantly associated with female, low education level, unstable employment, low household economic status, and advanced cancer stage. The most common coping strategies were as follows: among lifestyle changes, reducing spending on basic items and leisure activities (78.7%) and cutting back on essential household expenses (66.4%); among financial resource strategies, borrowing money from relatives or friends (49.1%) and withdrawing funds from retirement or savings accounts (34.1%); within treatment modifications, switching treatment facilities or doctors due to cost concerns (9.3%); and within support seeking, obtaining help from welfare or community organizations (18.8%). All strategies were significantly more likely to be used by patients with severe FT. Conclusions FT was highly prevalent among patients with cancer. Most patients relied on lifestyle adjustments and coping strategies, underscoring the need for improved financial support systems to alleviate the economic burden associated with cancer care.