ARTICLE ABSTRACTDesmoplastic reaction (DR) is one of many tumor-host interactions and is associated with the overall survival (OS) of patients with colorectal cancer (CRC). However, the clinical significance of DR requires further study in large multicenter cohorts and its predictive value in adjuvant chemotherapy (ACT) response remains unclear. Here, a total of 2225 CRC patients from five independent institutions were divided into primary (N=1012 from two centers) and validation (N=1213 from three centers) cohorts. DR were classified as immature, middle, or mature depending on the presence of myxoid stroma and hyalinized collagen bundles at the invasive front of the primary tumor. OS among different subgroups were compared, and the correlation of DR type with tumor infiltrating lymphocytes (TILs) within stroma, tumor stroma ratio (TSR) and Stroma AReactive Invasion Front Areas (SARIFA) were also analyzed. In the primary cohort, patients with mature DR had the highest 5-year survival rate. These findings were confirmed in validation cohort. Additionally, for stage II CRC, patients classified as non-mature DR would benefit from ACT compared with surgery alone. Furthermore, immature and middle DR were more associated with high TSR, less distribution of TILs within stroma and positive SARIFA compared to mature. Taken together, these data suggest that DR is a robust independent prognostic factor for CRC patients. For stage II CRC patients, non-mature DR could be a potential marker for recognizing high-risk patients who may benefit from ACT.