Peritoneal involvement in colorectal cancer (CRC) has prognostic significance and is an important parameter in pathologic tumor staging. Restaging of tumors based on peritoneal elastic lamina invasion (ELI) has prognostic significance in CRCs classified as pathologic stage 3 tumors without regional lymph node metastasis (pT3N0). However, limited data on the significance of ELI in patients with node-positive disease are available. We applied elastic stain to one block per case for 141 consecutive patients with pT3N1M0 CRCs. The elastic lamina was identified in only 62 cases (44%), of which 39 (27.6%) displayed ELI. The ELI+ group was associated with a significantly worse (0.;P <.001) 5-year disease-free survival (5-year DFS, 48.7%) and 5-year overall survival (5-year OS, 61.4%) compared with the ELI− (5-year DFS, 73.9%; OS, 95.7%) and no elastic lamina (5-year DFS, 79.5%; OS, 85.7%) groups. Comparison of outcomes in cases with pT3N1M0 with peritoneal ELI and pT4aN1M0 tumors (based on the original pathologic assessment without the use of elastic staining) showed no significant differences in the 5-year DFS (P =.47) and OS (P =.65). These findings suggest that ELI is a significant prognostic marker and that elastic staining should be considered for routine use in pT3 CRCs in a node-positive setting. Upstaging of pT3 tumors with ELI should be considered in the future iterations of the American Joint Committee on Cancer/Union for International Cancer Control tumor-node-metastasis staging system for CRC.