Background: The imbalanced allocation of medical resources leads to the occurrence of cross-regional healthcare-seeking in China. Due to the low cure rate, advanced colorectal cancer (CRC) patients may seek cross-regional healthcare for high-level medical facilities. Investigating status of cross-regional healthcare-seeking and its associated factors among advanced CRC patients is important for policymakers to understand access to health services and improve the quality of oncology services. Methods: From March 2020 to March 2021, a cross-sectional, nation-wide, hospital-based, multi-center survey was conducted. Nineteen hospitals in seven regions were selected by multi-stage stratified sampling.All eligible CRC patients in the selected hospitals were invited to participate in the current study. The outcome variable, cross-regional healthcare-seeking, was defined as seeking health facilities outside the local administration policy of medical insurance. The demographics, clinical information, and medical treatment history of each eligible CRC patient in stage III or IV, were collected through the patients' self-reporting or medical records by trained interviewers. Univariate and multivariate logistic analyses were used to explore the associated factors of cross-regional healthcare-seeking. All statistical analyses were conducted using SAS 9.4. Results: A total of 4,589 individuals with advanced CRC were included. The average age of the patients was 60.1 +/- 11.6 years, and 59.5% were males. About 37.5% of the patients suffered from metastatic CRC at first diagnosis. Approximately 36.5% of the patients had sought cross-regional health care previously, and among them, 31.9% had encountered problems. The most common problems included complicated procedures (95.3%), unreimbursed expenses of outpatient service (71.0%), and reimbursement delay (59.4%). Logistic regression analysis showed that patients who completed undergraduate or above [odds ratio (OR) =1.40, 95% confidence interval (CI): 1.13-1.73], had an annual household income of more than 100,000 Chinse Yuan (CNY) (OR =1.46, 95% CI: 1.21-1.78), and had metastasis at diagnosis (OR =1.33, 95% CI: 1.18-1.51) were more likely to seek cross-regional health care. Conclusions: About one third of advanced CRC patients seek cross-regional health care, and 31.9% had encountered problems. There is a need to simplify procedures of reimbursement, optimize direct settlement system and referral mechanisms in order to improve the equality of health services.