Objectives: This study aimed to investigate the association between adjuvant chemotherapy and prognosis of cancer-associated venous thromboembolism in patients with colorectal cancer. Methods: In this study, open data for secondary analyses were obtained from the DATADRYAD website (www.datadryad.org), and primary data were obtained from Sapporo City General Hospital, Japan. A total of 289 colorectal cancer (CRC) were included in this study. Cancer-associated venous thrombosis was diagnosed by reviewing all reports of enhanced Computed Tomography (CT) performed during follow-up. The association between adjuvant chemotherapy and cancer-associated venous thromboembolism was analyzed using a COX regression model. Survival curves and subgroup analyses were performed to ensure the stability of the results. Results: After adjusting for confounders, the risk of thromboembolism for patients in the group receiving adjuvant chemotherapy was (HR=3.45, 95% CI: 1.46~8.15, P<0.05) compared with the group without adjuvant chemotherapy; the survival curve showed that the prognosis for cancer-associated venous thromboembolism was worse in the group receiving adjuvant chemotherapy. Subgroup analysis showed that the association between adjuvant chemotherapy and the risk of cancer-associated venous thromboembolism remained stable. Conclusions: In the colorectal cancer population, patients receiving chemotherapy who developed cancer-associated venous thromboembolism had a worse prognosis.