Introduction: Biological medicines have increased the cost of cancer treatments, which also raises concerns about sustainability. In Brazil, three monoclonal antibodies (mAbs)—bevacizumab, cetuximab, and panitumumab—are indicated for the treatment of metastatic colorectal cancer (mCRC) but not currently funded by the Unified Health System (SUS). However, successful litigation has led to funding in some cases. Objective: Our objective was to evaluate the budgetary impact of including the mAbs bevacizumab, cetuximab, and panitumumab in standard chemotherapy for the treatment of mCRC within the SUS of Minas Gerais (MG), Brazil. Method: A budget impact analysis of incorporating mAbs as first-line treatment of mCRC in MG was explored. The perspective taken was that of the Brazilian SUS, and a 5-year time horizon was applied. Data were collected from lawsuits undertaken between January 2009 and December 2016, and the model was populated with data from national databases and published sources. Costs are expressed in $US. Results: In total, 351 lawsuits resulted in funding for first-line treatment with mAbs for mCRC. The three alternative scenarios analyzed resulted in cost increases of 348–395% compared with the reference scenario. The use of panitumumab had a budgetary impact of $US103,360,980 compared with the reference scenario over a 5-year time horizon, and bevacizumab and cetuximab had budgetary impacts of $US111,334,890 and 113,772,870, respectively. The use of the anti-epidermal growth factor receptor (EGFR) mAbs (cetuximab and panitumumab) is restricted to the approximately 41% of patients with KRAS mutations, so the best cost alternative for incorporation would be the combination of panitumumab and bevacizumab, with a cost of approximately $US106 million. Conclusion: These results highlight the appreciable costs for incorporating bevacizumab, cetuximab, and panitumumab into the SUS. Appreciable discounts are likely to be necessary before incorporation of these mAbs is approved.