BACKGROUND: Appendiceal tumors comprise a heterogeneous group of tumors that may be localized or disseminated throughout the peritoneum. Limited high-quality clinical data exist, and many practices have been extrapolated from colorectal cancer without validation in appendiceal cohorts. There are many controversies regarding the treatment of appendiceal tumors, and practices vary widely between centers and care settings. A national consensus update of best management practices for appendiceal malignancies was performed to better standardize care. METHODS: The 2018 Chicago Consensus guideline was updated through a modified Delphi consensus performed over two rounds using nationally circulated surveys. Supporting evidence was evaluated using rapid systematic reviews. Key systemic therapy concepts were summarized by content experts. RESULTS: Most supporting literature consists of observational studies, but high-quality studies increasingly are becoming available to drive management. Two consensus-based pathways were generated for localized appendiceal tumors: one for epithelial mucinous neoplasms and another for appendiceal adenocarcinoma. Of 138 participants responding in the first round, 133 (96%) engaged in the second round. Greater than 90% consensus was achieved for all pathway blocks. Key points include minimizing intervention invasiveness when permitted by pathologic classification and margin status and determining which margin and pathologic findings are indications for consideration of cytoreduction with or without intraperitoneal chemotherapy. Surveillance and systemic therapy recommendations are also presented. CONCLUSIONS: With growing but still primarily observational evidence currently dictating care, these consensus recommendations provide expert guidance in the treatment of appendiceal tumors without peritoneal involvement.